EXJ_799 jeep xj service manual

7/29/2019 EXJ_799 jeep xj service manual

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COOLING SYSTEM

CONTENTS

page page

GENERAL INFORMATIONACCESSORY DRIVE BELT TENSION . . . . . . . . . 3

COOLANT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2COOLING SYSTEM COMPONENTS . . . . . . . . . . 2COOLING SYSTEM . . . . . . . . . . . . . . . . . . . . . . 1ENGINE ACCESSORY DRIVE BELTS . . . . . . . . . 1ENGINE BLOCK HEATER . . . . . . . . . . . . . . . . . 3

RADIATORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2SYSTEM COOLANT ROUTING . . . . . . . . . . . . . 2WATER PUMPS . . . . . . . . . . . . . . . . . . . . . . . . . 2

DESCRIPTION AND OPERATION

ACCESSORY DRIVE BELT TENSION . . . . . . . . . 4AUTOMATIC TRANSMISSION OIL COOLER . . . 3AUXILIARY ELECTRIC COOLING FAN . . . . . . . . 8COOLANT PERFORMANCE . . . . . . . . . . . . . . . . 5

COOLANT RESERVE/OVERFLOW SYSTEM . . . 3COOLANT SELECTION-ADDITIVES . . . . . . . . . . 5COOLING SYSTEM FANS . . . . . . . . . . . . . . . . . 4COOLING SYSTEM HOSES . . . . . . . . . . . . . . . . 6

ENGINE BLOCK HEATER . . . . . . . . . . . . . . . . . 4RADIATOR PRESSURE CAP . . . . . . . . . . . . . . . 5THERMOSTAT . . . . . . . . . . . . . . . . . . . . . . . . . . 4VISCOUS FAN DRIVE . . . . . . . . . . . . . . . . . . . . 7

WATER PUMPS . . . . . . . . . . . . . . . . . . . . . . . . . 6

DIAGNOSIS AND TESTINGAUXILIARY ELECTRIC COOLING FAN . . . . . . . 21COOLING SYSTEM DIAGNOSIS . . . . . . . . . . . 12DEAERATION . . . . . . . . . . . . . . . . . . . . . . . . . 22

DRB SCAN TOOL . . . . . . . . . . . . . . . . . . . . . . . 8ENGINE ACCESSORY DRIVE BELTS . . . . . . . . . 9LOW COOLANT LEVEL-AERATION . . . . . . . . . 22ON-BOARD DIAGNOSTICS (OBD) . . . . . . . . . . . 8

PRELIMINARY CHECKS . . . . . . . . . . . . . . . . . 10PRESSURE TESTING RADIATOR CAPS . . . . . 22RADIATOR CAP-TO-FILLER NECK SEAL

PRESSURE RELIEF CHECK . . . . . . . . . . . . . 21

RADIATOR COOLANT FLOW CHECK . . . . . . . 19TESTING COOLING SYSTEM FOR LEAKS . . . 19

VISCOUS FAN DRIVE . . . . . . . . . . . . . . . . . . . 20SERVICE PROCEDURES

ADDING ADDITIONAL COOLANTROUTINE . . 22COOLANT LEVEL CHECKROUTINE . . . . . . . 22COOLANT LEVEL CHECKSERVICE . . . . . . . 22

COOLANT SERVICE . . . . . . . . . . . . . . . . . . . . 22DRAINING AND FILLING COOLING SYSTEM . . 23REVERSE FLUSHING . . . . . . . . . . . . . . . . . . . 23

REMOVAL AND INSTALLATION

AUXILIARY ELECTRIC COOLING FAN . . . . . . . 34COOLANT RESERVE TANK . . . . . . . . . . . . . . . 25COOLING SYSTEM FANS . . . . . . . . . . . . . . . . 37ENGINE ACCESSORY DRIVE BELTS . . . . . . . . 34

ENGINE BLOCK HEATER . . . . . . . . . . . . . . . . 34RADIATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30THERMOSTAT . . . . . . . . . . . . . . . . . . . . . . . . . 29TRANSMISSION OIL COOLERS . . . . . . . . . . . . 24

VISCOUS FAN DRIVE REMOVAL/INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . 38

WATER PUMP . . . . . . . . . . . . . . . . . . . . . . . . . 25CLEANING AND INSPECTION

COOLING SYSTEM CLEANING . . . . . . . . . . . . 38

COOLING SYSTEM HOSES . . . . . . . . . . . . . . . 38FAN BLADE INSPECTION . . . . . . . . . . . . . . . . 38RADIATOR CLEANING . . . . . . . . . . . . . . . . . . . 38RADIATOR PRESSURE CAP . . . . . . . . . . . . . . 38

SPECIFICATIONSBELT TENSION . . . . . . . . . . . . . . . . . . . . . . . . 38COOLING SYSTEM CAPACITIES . . . . . . . . . . . 38TORQUE SPECIFICATIONS . . . . . . . . . . . . . . . 39

SPECIAL TOOLSCOOLING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

GENERAL INFORMATION

ENGINE ACCESSORY DRIVE BELTS

CAUTION: When installing a serpentine accessory

drive belt, the belt MUST be routed correctly. If not,the engine may overheat due to water pump rotat-ing in wrong direction. Refer to the appropriateengine Belt Schematic in this group for the correct

belt routing. Or, refer to the Belt Routing Labellocated in the engine compartment.

COOLING SYSTEMThe cooling system regulates engine operating tem-

p e r a t u r e . I t a l lo w s t h e e n g in e t o r e a ch n o r m a l o p e r -

a t in g t e m p e r a t u r e a s q u ick ly a s p o ssible , m a in t a in s

n or m a l op er a t i n g t e m pe ra t u r e a n d p re ve nt s ov er -

h e a t in g .

The cooling syst em a lso provides a means of heat-

ing the passenger compartment and cooling the auto-

ma tic tra nsmission fluid (if equipped). The cooling

s y s t em i s p re ss u ri ze d a n d u s es a ce nt r i fu g a l w a t e r

pump to circulate coolant throughout the system.

XJ COOLING SYSTEM 7 - 1


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An op t ion a l f a ct or y in st a l led h e a vy d u t y coolin g

p a cka g e is a va i la ble on m ost m o de ls. Th e p a cka g e

con s is t s of a r a d i a t or t h a t h a s a n i n cr ea s e d n u m b er

of cooling fins. Vehicles equ ipped wit h a 4.0L 6- cyl-

inder engine a nd heavy duty cooling a nd/or a ir con-

dit ioning also have an auxiliary electric cooling fan.

COOLING SYSTEM COMPONENTSThe cooling system consists of:

A r a d ia t or

Cooling fan (mechan ical a nd/or electrica l)

Thermal viscous fan drive

F a n sh r o u d

Ra d ia t or p r essu r e ca p

Thermostat

Coola nt reserve/overflow syst em

Tr a n sm ission oi l cooler (i f e q u ip pe d w it h a n

a u t o m a t ic t r a n sm ission )

Coolant

Wa ter pump H o ses a n d h ose cla m p s

SYSTEM COOLANT ROUTINGFor cooling syst em flow routings, refer t o (Fig. 1)

(Fig. 2).

WATER PUMPSA quick test to determine if the pump is working is

t o che ck i f t h e h e a t e r w a r m s p r op er ly. A d e fe ct ive

w a t e r p u m p w ill n o t be a ble t o cir cu la t e h e a t e d cool-

a n t t h r o u g h t h e lo n g h e a t e r h o se t o t h e h e a t e r co r e .

COOLANTThe cooling syst em is designed around the coolan t .C ool a n t f low s t h r ou gh t h e en g in e w a t e r ja c ket s

a bso r bin g h e a t p r od u ce d d u r ing e n gin e op er a t io n .

Th e c ool a n t ca r r i es h ea t t o t h e r a d ia t o r a n d h ea t e r

co r e . H e r e i t is t r a n sf e r r e d t o t h e a m bie n t a ir p a ss-

i n g t h r ou g h t h e r a d i a t or a n d h ea t e r cor e f in s . Th e

co o la n t a lso r e m o ve s h e a t f r o m t h e a u t o m a t ic t r a n s-

mission fluid in vehicles equipped with an automatic

transmission.

RADIATORS2.5L 4cylinder engine radiators are the down flow

t y p e, 4.0L 6-cy lin d e r e n gin e r a d ia t o r s a r e t h e cr ossf lo w t y p e . Pla st ic t a n k s a r e u se d o n a l l r a d ia t o r s.

CAUTION: Plastic tanks, while stronger than brass,are subject to damage by impact, such aswrenches.

Fig. 1 Coolant Flow2.5L 4-Cylinder EngineTypical

TO COOLANT RECOVERYBOTTLE RADIATOR LOWERHOSEWATER PUMP PULLEYRADIATORRADIATOR UPPER HOSETO WATER PUMPHEATER CORE

7 - 2 COOLING SYSTEM XJ

GENERAL INFORMATION (Continued)


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I f t h e p l a s t i c t a n k h a s b e e n d a m a g e d , t h e p l a s t i c

ta nk an d/or o-rings ar e a vailable for service repair .Tank replacement sh ould be done by a qua lified per-

son with proper equipment.

ACCESSORY DRI VE BELT TENSIONCorrect accessory drive belt t ension is required t o

e n sur e op t im u m p er f or m a n ce of belt d r ive n e n gin e

a cce ssor ies. I f sp ecif ie d t e n sion is n ot m a in t a in ed ,

belt slippage may cause: engine overheating, lack of

power steering assist , loss of air conditioning capac-

it y, r e du ce d g en e r a t o r ou t p u t r a t e , g r ea t ly r e d uce d

belt life and objectionable under hood noise.

DOMESTIC LEFT HAND DRIVE VEHICLESB e lt t en s ion i s a d ju st ed a t t h e pow e r s t eer in g

pump bracket and idler pulley assembly.

DOMESTIC RIGHT HAND DRIVE VEHICLES

If equipped with a 4.0L 6-cylinder engine; the ser-

p en t i n e b e lt i s a d ju s t ed a t t h e g en er a t o r m ou n t in g

b r a ck et . Wh en e q ui pp ed w i t h a 2. 5L 4-cy l in d er

e n g in e , t h e se r p e n t in e be lt is a d ju st e d a t t h e p o w e r

steering pump bracket and idler pulley assembly.

ENGINE BLOCK HEATERAn optional engine block heater is available for all

m o de ls. Th e h e a t e r is e q u ip pe d w it h a p ow e r cor d .

The cord is at tached to an engine compartment com-

ponent with t ie-straps. The heater warms the engine

p r o vid in g e a sie r e n g in e st a r t in g a n d f a st e r w a r m - u p

in low temperatures. The heater is mounted in a corehole of the engine cylinder block (in place of a freeze

p lu g ) w it h t h e h e a t in g e le m en t im m er sed in e n gin e

coolan t . Connect the power cord to a grounded 110-

120 volt AC electrical outlet with a grounded, three-

wire extension cord.

DESCRIPTION AND OPERATION

AUTOM ATIC TRANSMI SSION OIL COOLER

WATER-TO-OIL COOLER

All m o d els e q u ipp ed w it h a n a u t o m a t ic t r a n sm is-s i on a r e e q ui pp ed w i t h a t r a n s m i ss ion oi l cool er

m ou n t ed i n t er n a l ly w i t h in t h e r a d i a t or t a n k . Th i s

internal cooler is supplied as standard equipment on

a ll m od e ls e q u ip pe d w it h a n a u t o m a t ic t r a n sm ission .

Tran smission oil is cooled w hen it passes through

t h is se p a r a t e cooler. I n ca se of a lea k in t h e in t e r n a l

radiator mounted transmission oil cooler, engine cool-

a n t m a y b ecom e m i xe d w i t h t r a n s m i ss ion f lu id or

transmission fluid may enter engine cooling system.

B o t h cool in g s y st em a n d t r a n sm is si on s h ou ld b e

d ra i ned a n d in spect ed if t h e in t er na l r a dia t or

mounted transmission cooler is leaking.

AIR-TO-OIL COOLER

An a u x ilia r y a ir -t o -oil t r a n sm ission oi l cooler is

a va ila ble w it h m ost e n gin e p a cka g e s.

The auxiliary air-to-oil tra nsmission oil cooler is

located in front of th e r adia tor or A/C condenser (if

e q u ip p e d ) a n d be h in d t h e g r i l l . I t is m o u n t e d t o t h e

front frame crossmember.

The auxiliary oil coolers on all models operate in

con ju n ct ion w it h t h e in t er n a l r a d ia t or m ou n t e d m a in

oil cooler. The transmission oil is routed through the

m a in cooler f ir st , t h e n t h e a u x ilia r y cooler, bef or e

r e t u r n in g t o t h e t r a n sm ission .

COOLANT RESERVE/OVERFLOW SYSTEMThe system works along with the radiator pressure

ca p . Th i s i s d on e b y u s in g t h er m a l e xp a n s ion a n d

contraction of the coolant to keep the coolant free of

trapped air . I t provides:

A volume for coolant expansion and contraction.

A convenient an d safe method for checking/ad-

justing coolant level at atmospheric pressure. This is

done without removing the radiator pressure cap.

S o me r es er v e cool a n t t o t h e r a d i a t or t o cov er

minor leaks and evaporation or boiling losses.

Fig. 2 Coolant Flow4.0L 6-Cylinder EngineTypical

HEATER CORETO COOLANT RESERVE/OVERFLOW TANKTHERMOSTATHOUSINGRADIATORWATER PUMP


GENERAL INFORMATION (Continued)


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As t h e en g in e cool s, a v a cu u m i s f or m ed i n t h e

cooling system of both the radiator and engine. Cool-

a n t w i ll t h en b e d r a w n f rom t h e c ool a n t t a n k a n d

returned to a proper level in the radiator.

The coolant reserve/overflow syst em consist s of a

r a d ia t or m ou n t e d p r essu r iz ed ca p , a p la st ic r e ser ve/

overflow tank (Fig. 3) (Fig. 4), a tube (hose) connect-i n g t h e r a d i a t o r a n d t a n k , a n d a n o v e r f l o w t u b e o n

t h e sid e o f t h e t a n k .

COOLING SYSTEM FANSAlso refer to either the Viscous Fa n Drive an d/or

the Auxiliary Electric Cooling Fan.

All models a re equipped wit h a mecha nical temper-

a t u r e co n t r o lle d f a n . T h is t h e r m a l visco u s f a n d r ive

is a torque-an d-temperature-sensit ive clutch unit . I t

a u t om a t i ca l l y i n cr ea s e s or d ecr ea s e s f a n s pe ed t o

provide proper engine cooling. Vehicles with a 4.0L

6-cylinder engine may also have an auxiliary electri-

ca l cool in g f a n ; w h e n eq u ip pe d a i r con d it i on i ng

a nd/or hea vy dut y cooling.

ACCESSORY DRI VE BELT TENSIONB o t h t h e 2.5l a n d 4.0l e n gin es u se o n e a cce ssor y

d r ive belt . C o rr e ct d r ive belt t e n sion is r e q u ir e d t o

en s ur e opt i mu m per for m a n ce of t h e b el t d r iv en

e ng in e a c ces s or i es . Th er e a r e d if fe re nt t y pe s of

a d ju st m en t g a u g e s f or ch eck in g e i t h er a ser p en t in e

or a conventional V-type belt . Refer to t he inst ruc-

t i o n s s u p p l i e d w i t h t h e g a u g e . M a k e s u r e t o u s e a

gauge designed specifically for serpentine style belts.

Place gauge in the middle of the section of belt being

tested (between t wo pulleys) to check tension. Do not

a l l ow t h e g a u g e (or g a u g e a d a p t er ) t o con t a c t a n y -

t h in g bu t t h e be lt .

ENGINE BLOCK HEATERAn optional engine block heater is available for all

m o de ls. Th e h e a t e r is e q u ip pe d w it h a p ow e r cor d .

The cord is at tached to an engine compartment com-

ponent with t ie-straps. The heater warms the enginep r o vid in g e a sie r e n g in e st a r t in g a n d f a st e r w a r m - u p

in low temperatures. The heater is mounted in a core

hole of the engine cylinder block (in place of a freeze

p lu g ) w it h t h e h e a t in g e le m en t im m er sed in e n gin e

coolan t . Connect the power cord to a grounded 110-

120 volt AC electrical outlet with a grounded, three-

wire extension cord.

WARNING: DO NOT OPERATE ENGINE UNLESS

BLOCK HEATER CORD HAS BEEN DISCONNECTEDFROM POWER SOURCE AND SECURED IN PLACE.

BLOCK HEATER SPECIFICATIONS 2.5L 4-Cylind er En gine: 115 Volts 400 Wa tt s

4.0L 6-Cylind er En gine: 120 Volts 600 Wa tt s

THERMOSTATA p e llet -t y p e t h e r m ost a t con t r ols t h e op er a t in g

temperature of the engine by controlling the amount

of cool a n t f low t o t h e r a d i a t or. O n a l l e ng in es t h e

thermostat is closed below 195F (90 C). Above this

t e m p e r a t u r e , co o la n t is a l lo w e d t o f lo w t o t h e r a d ia -

tor. This provides quick engine warm-up and overall

temperature control.

Fig. 3 Reserve/Overflow TankExcept Right HandDrive

Fig. 4 Reserve/Overflow TankWith Right HandDrive

CLAMP COOLANTRESERVE/OVERFLOWTANKMOUNTINGBOLTS LOWERBRACKETTUBE TO RADIATOR


DESCRIPTION AND OPERATION (Continued)


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An a r r ow pl us t h e w or d UP i s s t a m p ed on t h ef r on t f la n g e n ex t t o t h e a i r b le ed . Th e w o rd s TORAD a r e s t a m ped on on e a r m of t h e t h e rm os t a t .They indicate the proper installed posit ion.

T h e sa m e t h e r m o st a t is u se d f o r w in t e r a n d su m -

mer seasons. An engine should not be operated with-

ou t a t h er m os t a t , e xce pt f or s er v ici n g or t e st i n g.O pe r a t in g w it h ou t a t h e r m ost a t ca u ses ot h e r p r ob-

lems. These are: longer engine warm-up t ime, unre-

l ia b l e w a r m -u p p er f or m a n ce , i n cr ea s e d e xh a u s t

emissions and crankcase condensation. This conden-

sation can result in sludge formation.

CAUTION: Do not operate an engine without athermostat, except for servicing or testing.

COOLANT PERFORMANCE

ETHYLENE-GLYCOL MIXTURES

The required ethylene-glycol (antifreeze) and water

mixture depends upon the climate and vehicle oper-

a ting condit ions. The recommend ed mixtur e of 50/50

e t h y le n e-g ly col a n d w a t e r w il l p r ovid e p r ot e ct ion

against freezing to -37 deg. C (-35 deg. F). The anti-

freeze concentration must always be a m in im u m o f44 percent, year-round in all climates. If percentageis lower than 44 percent, engine parts may beeroded by cavitation, and cooling system com-ponents may be severely damaged by corrosion.M a x im u m p rot e ct i on a g a i n s t f r ee zi n g i s p rov id ed

w i t h a 68 p er ce nt a n t i f re ez e con ce nt r a t i on , w h i ch

prevents freezing down to -67.7 deg. C (-90 deg. F). Ah ig h er p er cen t a g e w il l f r e ez e a t a w a r m e r t e m p er a -

t u r e. Al so, a h i gh er p er ce nt a g e of a n t i f re ez e ca n

ca u s e t h e en g in e t o ov er h ea t b eca u s e t h e s peci fi c

h e a t o f a n t i f r e e z e is lo w e r t h a n t h a t o f w a t e r .

100 Percent Ethylene-Glycol Should Not Be Used inChrysler Vehicles

Use of 100 percent ethylene-glycol w ill cause for-

mation of addit ive deposits in the system, as the cor-

rosion inhibit ive a ddit ives in ethylene-glycol require

the presence of water to dissolve. The deposits act as

in su la t ion , ca u sin g t e m p er a t u r e s t o r ise t o a s h ig h a s

149 d e g. C (300) d eg . F ). Th is t e m pe r a t u r e is h oten ou gh t o m elt pla s t ic a n d s of ten s old er. Th e

in cr e a sed t e m pe r a t u r e ca n r e su lt in e n g in e d e t on a -

tion. In addit ion, 100 percent ethylene-glycol freezes

at 22 deg. C (-8 deg. F ).

Propylene-glycol Formulations Should Not Be Used i nChrysler Vehicles

Propylene-glycol formulations do not meetChrysler coolant specifications. It s overall effec-t ive t e m p e r a t u r e r a n g e is sm a lle r t h a n t h a t o f e t h y l-

ene-glycol. The freeze point of 50/50 propylene-glycol

and water is -32 deg. C (-26 deg. F). 5 deg. C higher

than ethylene-glycols freeze point. The boiling point

(protection aga inst summer boil-over) of propylene-

glycol is 125 deg. C (257 deg. F ) at 96.5 kPa (14 psi),

compared to 128 deg. C (263 deg. F) for ethylene-gly-

col. Use of propylene-glycol can result in boil-over or

freeze-up in Chrysler vehicles, which are designed forethylene-glycol. Propylene glycol also has poorer heat

t r a n sf e r ch a r a ct er ist ics t h a n e t h y le n e g ly col . Th is

ca n in cr e a se cy l in d er h e a d t e m pe r a t u r e s u n d e r cer -

tain conditions.

Propylene-glycol/Ethylene-glycol Mixtures Should Not BeUsed in Chrysler Vehicles

P r op y le n e-g ly col/e t h y le n e-g ly col Mixt u r e s ca n

cause the destabilization of various corrosion inhibi-

t o r s, ca u sin g d a m a g e t o t h e va r iou s coolin g sy st e m

components. Also, once ethylene-glycol an d propy-

lene-glycol ba sed coolant s ar e mixed in the vehicle,

conventional methods of determining freeze point willn ot be a ccur a t e . B o t h t h e r e f r a ct ive in d e x a n d sp e-

cific gravity differ between ethylene glycol a nd propy-

lene glycol.

CAUTION: Richer antifreeze mixtures cannot bemeasured with normal field equipment and can

cause problems associated with 100 percent ethyl-ene-glycol.

COOLANT SELECTION- ADDITI VESCoolant should be maintained at the specified level

w it h a m ixt u r e of e t h y le n e g ly col-ba se d a n t i f re ez ea n d l ow m in er a l con t en t w a t e r. O nl y u se a n a n t i -

freeze containing ALUGARD 340-2 .

CAUTION: Do not use coolant additives that areclaimed to improve engine cooling.

RADIATOR PRESSURE CAPAl l r a d i a t or s a r e eq u ip ped w i t h a p re ss u r e c a p .

Th i s ca p r el ea s e s p res s ur e a t s om e p oi n t w i t h in a

ra nge of 83-110 kP a (12-16 psi). The pressure relief

point (in pounds) is engraved on top of the cap (Fig.

5).

Th e cool in g s y st em w i ll oper a t e a t pr es su r es

slightly a bove a tmospheric pressure. This r esults in a

higher coolant boiling point allowing increased radi-

a t o r cool in g ca p a ci t y. Th e ca p con t a i n s a s pr i ng -

loa d e d p r essu r e r e lief va lve t h a t op en s w h e n sy st e m

pressure reaches release ra nge of 83-110 kP a (12-16

psi).

A v en t v a l ve i n t h e c en t er of ca p a l l ow s a s m a l l

coolant flow through cap when coolant is below boil-

ing temperature. The valve is completely closed when

boiling point is reached. As the coolan t cools, it con-




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t r a c t s a n d cr ea t e s a v a cu u m i n t h e c ool in g s y st e m .

This causes the vacuum valve to open and coolant in

t h e r e se r ve /over f low t a n k t o be d r a w n t h r o ug h i t s

con n e ct in g h ose in t o r a d ia t o r. I f t h e va cu u m va lve is

st u ck sh u t , t h e r a d ia t o r h ose s w ill colla p se on cool-

down.

A r u bbe r g a sk e t sea ls r a d ia t o r f il ler n e ck . Th is is

d on e t o m a in t a in va cu um d u r in g coola n t cool-d ow n

a n d t o p r ev en t l ea k a g e w h e n s y s t em i s u n d er p re s-

sure.

WATER PUMPSA cen t r if ug a l w a t e r p um p ci rcu la t e s cool a n t

t h r o ug h t h e w a t e r ja cke t s, p a ssa g e s, in t a k e m a n if old ,

radiator core, cooling system hoses and heater core.The pump is driven from the engine crankshaft by a

drive belt on all engines.

The water pump impeller is pressed onto the rear

of a s h a f t t h a t r ot a t e s i n b e a r in g s p r es s ed i n t o t h e

housing. The housing has a small hole to allow seep-

a g e t o e sca p e . T h e w a t e r p u m p se a ls a r e lu br ica t e d

b y t h e a n t i f re ez e i n t h e cool a n t m i xt u r e. N o a d d i-

tional lubrication is necessary.

CAUTION: All engines are equipped with a reverse(counter-clockwise) rotating water pump and vis-

cous fan drive assembly. REVERSE is stamped orimprinted on the cover of the viscous fan drive andinner side of the fan. The letter R is stamped intothe back of the water pump impeller (Fig. 6).

E n g i nes f r om p rev iou s m od el y ea r s , d ep en d in g

upon a pplicat ion, ma y ha ve been equipped w ith a for-

ward (clockwise) rotating water pump. Installat ion of

the wrong water pump will cause engine overheating.

A quick test to determine if the pump is working is

t o che ck i f t h e h e a t e r w a r m s p r op er ly. A d e fe ct ivewater pump will not be able to circulate heated cool-

a n t t h r o u g h t h e lo n g h e a t e r h o se t o t h e h e a t e r co r e .

COOLING SYSTEM HOSESRu bbe r h o se s r o u t e co o la n t t o a n d f r o m t h e r a d ia -

t o r , in t a k e m a n if o ld a n d h e a t e r co r e . Ra d ia t o r lo w e r

hoses ar e spring-reinforced to prevent collapse from

w a t e r p um p s uct ion a t m od er a t e a n d h ig h en g in e

speeds.

WARNING: CONSTANT TENSION HOSE CLAMPS

ARE USED ON MOST COOLING SYSTEM HOSES.

WHEN REMOVING OR INSTALLING, USE ONLYTOOLS DESIGNED FOR SERVICING THIS TYPE OFCLAMP, SUCH AS SPECIAL CLAMP TOOL (NUMBER

6094) (Fig. 7). SNAP-ON CLAMP TOOL (NUMBERHPC-20) MAY BE USED FOR LARGER CLAMPS.ALWAYS WEAR SAFETY GLASSES WHEN SERVIC-ING CONSTANT TENSION CLAMPS.

Fig. 5 Radiator Pressure Cap and Filler NeckTypical

TOP VIEWPRESSURE RATINGCROSS-SECTIONAL VIEW FILLER NECK SEALPRESSURE VALVEVACUUM VENT VALVE (SHOWN IN SEAL-ING POSITION)

Fig. 6 Reverse Rotating Water PumpTypical

FRONT VIEWROTATION DIRECTION ASVIEWED BACK VIEWROTATION DIRECTION ASVIEWEDR STAMPED INTO IMPELLER




7/40

CAUTION: A number or letter is stamped into thetongue of constant tension clamps (Fig. 8). Ifreplacement is necessary, use only an originalequipment clamp with matching number or letter.

I n s pe ct t h e h os es a t r eg u la r i n t er v a l s. R ep la c e

hoses that are cracked, feel brit t le when squeezed, or

swell excessively when the system is pressurized.

F or a l l v eh i cl es : I n a r e a s w h e r e s pe ci fi c r ou t i ng

clamps are not provided, be sure that hoses are posi-

t i on ed w i t h s u ff ici en t cl ea r a n c e. C h eck cl ea r a n c e

f r om e xh a u st m a n if old s a n d p ip e, f a n bla d es, d r ive

belts and sway bars. Improperly posit ioned hoses can

b e d a m a g e d, r es u lt i n g i n cool a n t l os s a n d en g in e

overheating.

Or din a r y w or m g ea r t y pe h os e cla m ps (w h en

eq u ip ped ) c a n b e r em ov ed w i t h a s t r a i gh t s cr ew -

d r iv er or a h ex s ock et . To prevent damage tohoses or clamps, the hose clamps should betightened to 4 Nm (34 in. lbs.) torque. Do notover tighten hose clamps.

VISCOUS FAN DRIVE

NOTE: Also refer to Cooling System Fans.

Th e t h e r m a l viscou s f a n d r ive is a s i licon e -f luid -

f il le d cou pl in g u s ed t o con n ect t h e f a n b la d e s t o

e it h e r t h e e n g in e o r t h e w a t e r p u m p sh a f t . T h e co u -

pling allows the fan to be driven in a normal manner.

This is done at low engine speeds while limiting the

t op s pe ed of t h e f a n t o a p re de t er m in ed m a x im u m

level at higher engine speeds.

A thermostatic bimetallic spring coil is located on

t h e f r on t f a ce of t h e viscou s f a n d r ive u n it . A t y p ica lviscou s u n it is sh ow n in (F ig . 9). Th is sp rin g coil

r e a c t s t o t h e t e m p e r a t u r e o f t h e r a d i a t o r d i s c h a r g e

a i r. I t e ng a g es t h e v is cou s f a n d r iv e f or h i gh er f a n

sp e e d i f t h e a ir t e m p e r a t u r e f r o m t h e r a d ia t o r r ise s

above a certain point . Until addit ional engine cooling

i s n e ce ss a r y, t h e f a n w i ll r em a i n a t a r ed u ce d r p m

regardless of engine speed.

O n ly w h e n su f f icie n t h e a t is p r e se n t , w il l t h e vis-co u s f a n d r ive e n g a g e . T h is is w h e n t h e a ir f lo w in g

t h r ou g h t h e r a d i a t or cor e ca u s es a r ea c t ion t o t h e

bimetallic coil. I t then increases fan speed to provide

the necessary addit ional engine cooling.

Once the engine has cooled, the radiator discharge

t e mp er a t u r e w i l l d r op . Th e b im e t a ll ic coi l a g a i n

r e a ct s a n d t h e f a n sp e e d is r e d u ce d t o t h e p r e vio u s

disengaged speed.

Fig. 7 Hose Clamp ToolTypical

HOSE CLAMP TOOL6094 HOSECLAMP

Fig. 8 Clamp Number/Letter Location

TYPICAL CONSTANTTENSION HOSE CLAMPCLAMP NUMBER/LETTER LOCA-TION TYPICAL HOSE

Fig. 9 Typical Viscous Fan Drive

VISCOUS FAN DRIVE MOUNTING HUBTHER MOSTATICSPRI NG




8/40

CAUTION: Engines equipped with serpentine drivebelts have reverse rotating fans and viscous fandrives. They are marked with the word REVERSE todesignate their usage. Installation of the wrong fanor viscous fan drive can result in engine overheat-

ing.

CAUTION: If the viscous fan drive is replacedbecause of mechanical damage, the cooling fanblades should also be inspected. Inspect for fatigue

cracks, loose blades, or loose rivets that couldhave resulted from excessive vibration. Replace fanblade assembly if any of these conditions arefound. Also inspect water pump bearing and shaft

assembly for any related damage due to a viscousfan drive malfunction.

NOISE

It is normal for fan noise to be louder (roar-ing) when: The underhood t empera ture is above the engage-

ment point for the viscous drive coupling. This ma y

occur when ambient (outside air temperature) is very

high.

En g in e loa d s a n d t e m pe r a t u r e s a r e h ig h su ch a s

w h e n t o w in g a t r a i le r .

C o ol si licon e f lu id w it h in t h e f a n d r ive u n it is

b ei n g r ed is t r ib u t ed b a ck t o i t s n or m a l d is en g a g ed

(w a r m ) p osit ion . Th is ca n occu r d u r in g t h e f ir st 15

seconds to one minute after engine start-up on a cold

engine.

AUXILIARY ELECTRIC COOLING FANModels equipped with a 4.0L 6-cylinder engine may

a lso h a ve a n a u x il ia r y e le ct r ica l co o lin g f a n . T h is is

with models tha t ha ve air conditioning a nd/or heavy

duty cooling. The fan is controlled by the cooling fan

relay, which is located in the power distribution cen-

t e r (PD C ) (F ig . 10). F o r t h e lo ca t io n o f r e la y w it h in

t h e PD C , r e f e r t o t h e la be l o n PD C co ve r .

When coolan t tempera ture reaches a pproximat ely

103C (218F), or when air conditioning is requested,

t h e p ow e r t r a in con t r ol m od u le (P C M ) p rov id es a

g r ou n d p a t h f or t h e f a n r el a y. Th i s g r ou n d i s p ro-vided to the cooling fan relay through pin C2 of PCM

co n n e ct o r C 3. B a t t e r y vo lt a g e is t h e n a p p lie d t o t h e

f a n t h r ou g h t h e r el a y. Wh en cool a n t t e m pe ra t u r e

d r op s below a p p r ox im a t e ly 98 C (209F ), t h e P C M

opens the ground path to the relay. This will prevent

the cooling fan from being energized.

DIAGNOSIS AND TESTING

ON-BOARD DIAGNOSTICS (OBD)

COOLING SYSTEM RELATED DIAGNOSTICS

Th e P ow e r t r a in C o n t r ol Mod u le (P C M) h a s bee n

programmed to monitor the certain following cooling

system components:

I f t h e en g in e h a s r em a i n ed cool f or t oo l on g aperiod, such as with a stuck open thermostat , a Diag-

nostic Trouble Code (DTC) can be set .

If an open or shorted condition has developed in

the relay circuit controlling the electric radiator fan,

a Dia gnostic Trouble C ode (DTC) can be set .

I f t h e p rob lem i s s en s ed i n a m on i t or ed ci r cu it

often enough to indicate an actual problem, a DTC is

st o r e d . T h e D T C w il l be st o r e d in t h e PC M m e m o r y

for eventual display to the service technician. (Refer

t o G r o u p 25, E m ission C on t r o l S y st e m s f or p r op er

procedures)

ACCESSING DIAGNOSTIC TROUBLE CODESTo r e a d D TC s a n d t o o bt a in coolin g sy st e m d a t a ,

r ef er t o G r o up 25, E m i s si on C on t r ol S y s t em s f or

proper procedures.

DRB SCAN TOOLF or op er a t i on of t h e D R B s ca n t ool , r e fe r t o t h e

a p p r op r ia t e P ow e r t r a in D ia g n o st ic P r oce d ur e s se r-

vice m a n u a l .

Fig. 10 Power Distribution Center (PDC)

RIGHTFENDER BATTERYPOWER DISTRIBUTIONCENTER




9/40

ENGINE ACCESSORY DRIVE BELTS

BELT DIAGNOSIS

When diagnosing serpentine accessory drive belts,

sm a ll cr a ck s t h a t r u n a cr oss t h e r ibbe d su r f a ce of t h e

belt from rib to r ib (Fig. 11), are considered normal.

These are not a reason to replace the belt . However,cr a ck s r u n n in g a lo n g a r ib (n o t a cr o ss) a r e not nor-m a l. An y be lt w it h cr a ck s r u n n in g a lo n g a r ib m u st

be replaced (Fig. 11). Also replace the belt if it ha s

excessive wear, frayed cords or severe glazing.

R ef er t o t h e S er pen t in e D r iv e B e lt D i a gn os is

charts for further belt diagnosis.

SERPENTINE BELT DIAGNOSIS CHART

CONDITION POSSIBLE CAUSES CORRECTION

RIB CHUNKING (One or more ribs hasseparated from belt body)

1. Foreign objects imbedded in pulleygrooves.

1. Remove foreign objects from pulleygrooves. Replace belt.

2. Installation damage 2. Replace beltRIB OR BELT WEAR 1. Pulley misaligned 1. Align pulley(s)

2. Abrasive environment 2. Clean pulley(s). Replace belt ifnecessary

3. Rusted pulley(s) 3. Clean rust from pulley(s)

4. Sharp or jagged pulley groove tips 4. Replace pulley. Inspect belt.

5. Belt rubber deteriorated 5. Replace belt

BELT SLIPS 1. Belt slipping because of insufficienttension

1. Adjust tension

2. Belt or pulley exposed to substancethat has reduced friction (belt dressing,oil, ethylene glycol)

2. Replace belt and clean pulleys

3. Driven component bearing failure(seizure)

3. Replace faulty component or bearing

4. Belt glazed or hardened from heatand excessive slippage

4. Replace belt.

LONGITUDAL BELT CRACKING 1. Belt has mistracked from pulleygroove

1. Replace belt

2. Pulley groove tip has worn awayrubber to tensile member

2. Replace belt

Fig. 11 Serpentine Belt Wear Patterns


DIAGNOSIS AND TESTING (Continued)


10/40


GROOVE JUMPING(Belt does not maintain correctposition on pulley)

1. Belt tension either too low or toohigh

1. Adjust belt tension

2. Pulley(s) not within designtolerance

2. Replace pulley(s)

3. Foreign object(s) in grooves 3. Remove foreign objects fromgrooves

4. Pulley misalignment 4. Align component

5. Belt cordline is broken 5. Replace belt

BELT BROKEN(Note: Identify and correct problem

before new belt is installed)

1. Excessive tension 1. Replace belt and adjust tension tospecification

2. Tensile member damaged duringbelt installation

2. Replace belt

3. Severe misalignment 3. Align pulley(s)

4. Bracket, pulley, or bearing failure 4. Replace defective component andbelt

NOISE

(Objectional squeal, squeak, orrumble is heard or felt while drive belt

is in operation)

1. Belt slippage 1. Adjust belt

2. Bearing noise 2. Locate and repair3. Belt misalignment 3. Align belt/pulley(s)

4. Belt to pulley mismatch 4. Install correct belt

5. Driven component induced

vibration

5. Locate defective driven component

and repair

6. System resonant frequencyinduced vibration

6. Vary belt tension withinspecifications.

TENSION SHEETING FABRICFAILURE(Woven fabric on outside,circumference of belt has cracked orseparated from body of belt)

1. Tension sheeting contactingstationary object

1. Correct rubbing condition

2. Excessive heat causing wovenfabric to age

2. Replace belt

3. Tension sheeting splice hasfractured

3. Replace belt

CORD EDGE FAILURE

(Tensile member exposed at edges ofbelt or separated from belt body)

1. Excessive tension 1. Adjust belt tension

2. Belt contacting stationary object 2. Replace belt

3. Pulley(s) out of tolerance 3. Replace pulley

4. Insufficient adhesion betweentensile member and rubber matrix

4. Replace belt and adjust tension tospecifications

PRELIMINARY CHECKS

ENGINE COOLING SYSTEM OVERHEATING

Est a blish w h a t d r ivin g con d it ion s ca u sed t h e com -

plaint . Abnormal loads on the cooling system such as

t h e f o l lo w in g m a y be t h e ca u se :

PROLONGED IDLE, VERY HIGH AMBIENT TEMPERATURE,SLIGHT TAIL WIND AT IDLE, SLOW TRAFFIC, TRAFFICJAMS, HIGH SPEED OR STEEP GRADES.

D r ivin g t e ch n iq u es t h a t a vo id over h e a t in g a r e :

I d le w it h A/C of f w h e n t e m pe r a t u r e g a u g e is a t

e n d o f n o r m a l r a n g e .

Increasing engine speed for more air f low is rec-

ommended.

TRAILER TOWING:

Consult Trailer Towing section of own ers ma nua l.

Do not exceed limits.

AIR CONDITIONING; ADD-ON OR AFTER MARKET:

A m a x im u m cool in g p a ck a g e s h ou ld h a v e b ee n

ordered wit h vehicle if a dd-on or a fter ma rket A/C is

in st a l led . I f n ot , m a x im u m coolin g sy st e m com p o-

n en t s s h ou ld b e i n st a l l ed f or m od el i n vol ved p er

ma nufacturers specificat ions.

RECENT SERVICE OR ACCIDENT REPAIR:

D et er m in e i f a n y r ecen t s er vi ce h a s b een per -

f or m e d on ve hicle t h a t m a y e ff ect coolin g sy st e m .

This may be:




11/40

Engine adjustments (incorrect t iming)

Slipping engine a ccessory drive belt(s)

Brakes (possibly dragging)

C h a n g e d p a r t s . I n cor r e ct w a t e r p u m p o r p u m p

r ot a t in g in w r o n g d ir e ct ion d u e t o be lt n ot cor r e ct ly

routed

Reconditioned ra diat or or cooling sy stem refill-ing (possibly under filled or air trapped in system).

NOTE: If investigation reveals none of the previousitems as a cause for an engine overheating com-plaint, refer to following Cooling System Diagnosischarts.

Th e se ch a r t s a r e t o be u sed a s a q u ick -r e fe r en ce

only. Refer to the group text for information.




12/40

COOLING SYSTEM DIAGNOSIS


TEMPERATURE GAUGE READSLOW

1. Has a Diagnostic Trouble Code(DTC) number 17 been set indicatinga stuck open engine thermostat?

1. Refer to On-Board Diagnostics inthe service manual text. Replacethermostat if necessary. If a

Diagnostic Trouble Code (DTC)number 17 has not been set, theproblem may be with the temperaturegauge.

2. Is the temperature gauge (ifequipped) connected to thetemperature gauge coolant sensor onthe engine?

2. Check the engine temperaturesensor connector in the enginecompartment. Refer to Group 8E.Repair as necessary.

3. Is the temperature gauge (ifequipped) operating OK?

3. Check gauge operation. Refer toGroup 8E. Repair as necessary.

4. Coolant level low in cold ambienttemperatures accompanied with poorheater performance.

4. Check coolant level in the coolantreserve/overflow tank and theradiator. Inspect system for leaks.Repair leaks as necessary. Refer tothe Coolant section of the manual text

for WARNINGS and precautionsbefore removing the radiator cap.

5. Improper operation of internalheater doors or heater controls.

5. Inspect heater and repair asnecessary. Refer to Group 24,Heating and Air Conditioning forprocedures.

TEMPERATURE GAUGE READSHIGH OR ENGINE COOLANTWARNING LAMP ILLUMINATES.COOLANT MAY OR MAY NOT BELOST OR LEAKING FROMCOOLING SYSTEM

1. Trailer is being towed, a steep hill isbeing climbed, vehicle is operated inslow moving traffic, or engine is beingidled with very high ambient (outside)temperatures and the air conditioningis on. Higher altitudes could aggravatethese conditions.

1. This may be a temporary conditionand repair is not necessary. Turn offthe air conditioning and attempt todrive the vehicle without any of theprevious conditions. Observe thetemperature gauge. The gaugeshould return to the normal range. Ifthe gauge does not return to normalrange, determine the cause for

overheating and repair. Refer toPOSSIBLE CAUSES (numbers 2through 20).

2. Is temperature gauge (if equipped)reading correctly?

2. Check gauge. Refer to Group 8E.Repair as necessary.

3. Is temperature warning lamp (ifequipped) illuminating unnecessarily?

3. Check warning lamp operation.Refer to Group 8E. Repair asnecessary.

4. Coolant low in coolant reserve/overflow tank and radiator.

4. Check for coolant leaks and repairas necessary. Refer to TestingCooling System For Leaks in thisgroup.

5. Pressure cap not installed tightly. Ifcap is loose, boiling point of coolant

will be lowered. Also refer to thefollowing step 6.

5. Tighten cap.

6. Poor seals at radiator cap. 6. (a) Check condition of cap and capseals. Refer to Radiator Cap. Replacecap if necessary.

(b) Check condition of radiator fillerneck. If neck is bent or damaged,replace radiator.

COOLING SYSTEM DIAGNOSIS




13/40


TEMPERATURE GAUGE READSHIGH OR ENGINE COOLANTWARNING LAMP ILLUMINATES.

COOLANT MAY OR MAY NOT BE

LOST OR LEAKING FROM COOLINGSYTEM (Continued)

7. Coolant level low in radiator but notin coolant reserve/overflow tank. Thismeans the radiator is not drawing

coolant from the coolant reserve/

overflow tank as the engine cools.As the engine cools, a vacuum isformed in the cooling system of theengine and radiator. If radiator cap

seals are defective, or cooling systemhas leaks, a vacuum can not beformed.

7. (a) Check condition of radiator capand cap seals. Refer to Radiator Capin this group. Replace cap if necessary.

(b) Check condition of radiator filler

neck. If neck is bent or damaged,replace radiator.(c) Check the condition of the hosefrom the radiator to the coolant tank. It

should fit tight at both ends without anykinks or tears. Replace hose ifnecessary.(d) Check coolant reserve/overflow

tank and tank hose for blockage.Repair as necessary.

8. Freeze point of antifreeze not

correct. Mixture may be too rich.

8. Check antifreeze. Refer to Coolant

section of this group. Adjust antifreeze-to-water ratio as required.

9. Coolant not flowing through system. 9. Check for coolant flow at radiatorfiller neck with some coolant removed,engine warm and thermostat open.Coolant should be observed flowing

through radiator. If flow is notobserved, determine reason for lack offlow and repair as necessary.

10. Radiator or A/C condenser fins aredirty or clogged.

10. Clean insects or debris. Refer toRadiator Cleaning in this group.

11. Radiator core is corroded or

plugged.

11. Have radiator re-cored or replaced.

12. Aftermarket A/C installed without

proper radiator.

12. Install proper radiator.

13. Fuel or ignition system problems. 13. Refer to Fuel and Ignition Systemgroups for diagnosis. Also refer to the

appropriate Powertrain DiagnosticProcedures service manual foroperation of the DRB scan tool.

14. Dragging brakes. 14. Check and correct as necessary.Refer to Group 5, Brakes in thismanual text.

15. Bug screen is being used reducingairflow.

15. Remove bug screen.

16. Thermostat partially or completelyshut. This is more prevalent on high

mileage vehicles.

16. Check thermostat operation andreplace as necessary. Refer to

Thermostats in this group.17. Thermal viscous fan drive notoperating properly.

17. Check fan drive operation andreplace if necessary. Refer to ViscousFan Drive in this group.

18. Electric cooling fan not operatingproperly (XJ models with 4.0L engineequipped with heavy duty cooling

and/or air conditioning).

18. Check electric fan operation andrepair as necessary. Refer to AuxiliaryElectric Cooling Fan-XJ Models with

4.0L 6-cylinder engine in the manualtext.

COOLING SYSTEM DIAGNOSIS (CONT.)




14/40


TEMPERATURE GAUGE READSHIGH OR ENGINE COOLANTWARNING LAMP ILLUMINATES.

COOLANT MAY OR MAY NOT BE

LOST OR LEAKING FROM COOLINGSYSTEM (Continued)

19. Cylinder head gasket leaking 19. Check for cylinder head gasketleaks. Refer to Testing Cooling Systemfor Leaks in this group. For repair refer

to Group 9, Engines.

20. Heater core leaking. 20. Check heater core for leaks. Referto Group 24, Heating and AirConditioning. Repair as necessary.

TEMPERATURE GUAGE READING ISINCONSISTENT (FLUCTUATES,

CCLES OR IS ERRACTIC)

1. On XJ models equipped with a 4.0L6-cylinder engine, heavy duty cooling

and/or air conditioning, the gauge maycycle up and down. This is due to thecycling of the electric radiator fan.

1. A normal condition. No correction isnecessary. If gauge cycling is going

into the hot zone, check electric fanoperation and repair as necessary.Refer to Auxiliary Electric CoolingFan-XJ Models with 4.0L 6-cylinder

engine in the manual text.

2. During cold weather operation, withthe heater blower in the high position,

the gauge reading may drop slightly.

2. A normal condition. No correction isnecessary.

3. Temperature gauge or engine

mounted gauge sensor defective orshorted. Also, corroded or loose wiringin this circuit.

3. Check operation of gauge and repair

if necessary. Refer to Group 8E,Instrument Panel and Gauges.

4. Gauge reading rises when vehicle isbrought to a stop after heavy use(engine still running).

4. A normal condition. No correction isnecessary. Gauge reading shouldreturn to normal range after vehicle isdriven.

5. Gauge reading high after restarting awarmed-up (hot) engine.

5. A normal condition. No correction isnecessary. The gauge should return to

normal range after a few minutes ofengine operation.

6. Coolant level low in radiator (air willbuild up in the cooling system causing

the thermostat to open late).

6. Check and correct coolant leaks.Refer to Testing Cooling Sytem for

Leaks in this group.

7. Cylinder head gasket leaking

allowing exhaust gas to enter coolingsystem causing thermostat to open late.

7. (a) Check for cylinder head gasket

leaks with a commercially availableBlock Leak Tester. Repair asnecessary.(b) Check for coolant in the engine oil.

Inspect for white steam emitting fromexhaust system. Repair as necessary.

8. Water pump impeller loose on shaft. 8. Check water pump and replace as

necessary. Refer to Water Pumps inthis group.

9. Loose accessory drive belt (water

pump slipping).

9. Refer to Engine Accessory Drive

Belts in this group. Check and correctas necessary.

10. Air leak on the suction side of waterpump allows air to build up in coolingsystem causing thermostat to open late.

10. Locate leak and repair asnecessary.





15/40


PRESSURE CAP IS BLOWING OFF

STEAM AND/OR COOLANT TOCOOLANT TANK. TEMPERATUREGAUGE READING MAY BE ABOVENORMAL BUT NOT HIGH. COOLANT

LEVEL MAY BE HIGH IN COOLANTRESERVE/OVERFLOW TANK

1. Pressure relief valve in radiator cap

is defective.

1. Check condition of radiator cap and

cap seals. Refer to Radiator Caps inthis group. Replace cap as necessary.

COOLANT LOSS TO THE GROUNDWITHOUT PRESSURE CAPBLOWOFF. GAUGE IS READINGHIGH OR HOT

1. Coolant leaks in radiator, coolingsystem hoses, water pump or engine.

1. Pressure test and repair asnecessary. Refer to Testing CoolingSystem for Leaks in this group.

DETONATION OR PREIGNITION(NOT CAUSED BY IGNITIONSYSTEM). GAUGE MAY OR MAY

NOT BE READING HIGH

1. Engine overheating. 1. Check reason for overheating andrepair as necessary.

2. Freeze point of antifreeze not

correct. Mixture is too rich or too lean.

2. Check antifreeze. Refer to the

Coolant section in this group. Adjustantifreeze-to-water ratio as required.

HOSE OR HOSES COLLAPSE WHENENGINE IS COOLING

1. Vacuum created in cooling system onengine cool-down is not being relievedthrough coolant reserve/overflow

system.

1. (a) Radiator cap relief valve stuck.Refer to Radiator Cap in this group.Replace if necessary.

(b) Hose between coolant reserve/overflow tank and radiator is kinked.Repair as necessary.(c) Vent at coolant reserve/overflow

tank is plugged. Clean vent and repairas necessary.(d) Reserve/overflow tank is internallyblocked or plugged. Check forblockage and repair as necessary.

ELECTRIC RADIATOR FAN RUNSALL THE TIME (XJ MODELS WITH

4.0L ENGINE EQUIPPED WITHHEAVY DUTY COOLING AND/OR AIRCONDITIONING ONLY)

1. Fan relay, powertrain control module(PCM) or engine coolant temperature

sensor defective.

1. Refer to Auxiliary Electric CoolingFan-XJ Models with 4.0L 6-Cylinder

engine in the manual text. Repair asnecessary. Also refer to appropriatePowertrain Diagnostic Proceduresservice manual for operation of the

DRB scan tool.

ELECTRIC RADIATOR FAN WILL NOT

RUN (XJ MODELS WITH 4.0LENGINE EQUIPPED WITH HEAVYDUTY COOLING AND/OR AIRCONDITIONING ONLY) GAUGEREADING HIGH OR HOT

1. Fan motor defective. 1. Refer to Auxiliary Electric Cooling

Fan-XJ Models with 4.0L 6-Cylinderengine in the manual text. Repair asnecessary.

2. Fan relay, powertrain control module(PCM) or engine coolant temperaturesensor defective.

2. Refer to Auxiliary Electric CoolingFan-XJ Models with 4.0L 6-Cylinderengine in the manual text. Repair asnecessary. Also refer to the appropriate

Powertrain Diagnostic Proceduresservice manual for operation of theDRB scan tool

3. Blown fuse in power distributioncenter (PDC).

3. Determine reason for blown fuseand repair as necessary.





16/40


NOISY FAN 1. Fan blades loose. Replace fan blade assembly. Refer toCooling System Fans in this group.

2. Fan blades striking a surroundingobject.

2. Locate point of fan blade contactand repair as necessary.

3. Air obstructions at radiator or airconditioning condenser. 3. Remove obstructions and/or cleandebris or insects from radiator or A/Ccondenser.

4. Electric fan motor defective (ifequipped).

4. Replace electric fan motor. Refer toAuxiliary Electric Cooling Fan-XJModels with 4.0L 6-Cylinder engine inthe manual text.

5. Thermal viscous fan drive hasdefective bearing.

5. Replace fan drive. Bearing is notserviceable. Refer to Viscous FanDrive in this group.

6. A certain amount of fan noise(roaring) may be evident on modelsequipped with a thermal viscous fan

drive. Some of this noise is normal.

6. Refer to Viscous Fan Drive in thisgroup for an explanation of normal fannoise.

INADEQUATE AIR CONDITIONERPERFORMANCE (COOLING SYSTEMSUSPECTED)

1. Radiator and/or A/C condenser isrestricted, obstructed or dirty (insects,leaves etc.).

1. Remove restriction and/or clean asnecessary. Refer to Radiator Cleaningin this group.

2. Electric radiator fan not operatingwhen A/C is operated (if equipped withelectric fan).

2. Refer to Auxiliary Electric CoolingFan-XJ Models with 4.0L 6-Cylinderengine in the manual text. Repair as

necessary.

3. Thermal viscous fan drive isfreewheeling.

3. Refer to Viscous Fan Drive fordiagnosis. Repair as necessary.

4. Engine is overheating (heat may betransferred from radiator to A/C

condenser. High underhoodtemperatures due to engine overheatingmay also transfer heat to A/Ccomponents).

4. Correct overheating condition. Referto text in Group 7, Cooling.

5. Some models with certain enginesare equipped with air seals at theradiator and/or A/C condenser. If these

seals are missing or damaged, notenough air flow will be pulled throughthe radiator and A/C condenser.

5. Check for missing or damaged airseals and repair as necessary.

INADEQUATE HEATERPERFORMANCE. THERMOSTAT

FAILED IN OPEN POSITION

1. Has a diagnostic trouble code (DTC)number 17 been set?

1. Refer to On-Board Diagnostics inthe manual text and replace thermostat

if necessary.2. Coolant level low. 2. Refer to Testing Cooling System forLeaks in the manual text. Repair as

necessary.

3. Obstructions in heater hose fittings at

engine.

3. Remove heater hoses at both ends

and check for obstructions. Repair asnecessary.

4. Heater hose kinked. 4. Locate kinked area and repair as

necessary.





17/40


INADEQUATE HEATERPERFORMANCE. THERMOSTATFAILED IN OPEN POSITION

(Continued)

5. Some models with certain enginesare equipped with a water controlvalve located on one of the heater

hoses. This valve may be defective.

5. Refer to Group 24, Heating andAir Conditioning for diagnosis. Repairas necessary.

6. Water pump is not pumping waterto heater core. When the engine is

fully warmed up, both heater hosesshould be hot to the touch. If onlyone of the hoses is hot, the waterpump may not be operating correctly.

The accessory drive belt may also beslipping causing poor water pumpoperation.

6. Refer to Water Pumps in thisgroup. Repair as necessary. If a

slipping belt is detected, refer toEngine Accessory Drive Belts in thisgroup. Repair as necessary.

HEAT ODOR 1. Various heat shields are used atcertain drive line components. One or

more of these shields may bemissing.

1. Locate missing shields andreplace or repair as necessary.

2. Is temperature gauge reading

above the normal range?

2. Refer to the previous Temperature

Gauge Reads High in theseDiagnosis Charts. Repair asnecessary.

3. Is cooling fan operating correctly? 3. Refer to Cooling System Fan inthis group for diagnosis. Repair asnecessary.

4. Has undercoating been applied toany unnecessary component?

4. Clean undercoating as necessary.

5. Engine may be running richcausing the catalytic convertor tooverheat.

5. Refer to the DRB scan tool andthe appropriate PowertrainDiagnostic Procedures service

manual. Repair as necessary.POOR DRIVEABILITY

(THERMOSTAT POSSIBLY STUCKOPEN) GAUGE READING MAY BELOW

1. For proper driveability, good

vehicle emissions and for preventingbuild-up of engine oil sludge, thethermostat must be operatingproperly. Has a diagnostic trouble

code (DTC) number 17 been set?

1. Refer to On-Board Diagnostics in

this group. DTCs may also bechecked using the DRB scan tool.Refer to the proper PowertrainDiagnostics Procedures service

manual for checking the thermostatusing the DRB scan tool. Replacethermostat if necessary.

STEAM IS COMING FROM FRONTOF VEHICLE NEAR GRILL AREA

WHEN WEATHER IS WET, ENGINE

IS WARMED UP AND RUNNING,AND VEHICLE IS STATIONARY.TEMPERATURE GAUGE IS IN

NORMAL RANGE

1. During wet weather, moisture(snow, ice or rain condensation) on

the radiator will evaporate when the

thermostat opens. This openingallows heated water into the radiator.When the moisture contacts the hot

radiator, steam may be emitted. Thisusually occurs in cold weather withno fan or airflow to blow it away.

1. Occasional steam emitting fromthis area is normal. No repair is

necessary.





18/40


COOLANT COLOR 1. Coolant color is not necessarily an

indication of adequate corrosion ortemperature protection. Do not relyon coolant color for determiningcondition of coolant.

1. Refer to Coolant in this group for

antifreeze tests. Adjust antifreeze-to-water ratio as necessary.

COOLANT LEVEL CHANGES INCOOLANT RESERVE/OVERFLOW

TANK. TEMPERATURE GAUGE ISIN NORMAL RANGE

1. Level changes are to be expectedas coolant volume fluctuates with

engine temperature. If the level in thetank was between the FULL and ADDmarks at normal engine operatingtemperature, the level should returnto within that range after operation at

elevated temperatures.

1. A normal condition. No repair isnecessary.





19/40

RADIATOR COOLANT FLOW CHECKThe following procedure will determine if coolant is

flowing through the cooling system.

If engine is cold, idle engine until norma l operat ing

temperature is reached. Then feel the upper radiator

h ose . I f h o se is h o t , t h e t h e r m ost a t is o pe n a n d w a t e r

is circulating through cooling system.

TESTING COOLING SYSTEM FOR LEAKS

ULTRAVIOLET LIGHT METHOD

Al l J e ep m od el s h a v e a l ea k d et e ct i on a d d i t iv e

added to th e cooling syst em before th ey leave th e fac-

tory. The addit ive is highly visible under ultraviolet

light (black light). I f the factory original coolant has

b ee n d r a i n ed , p ou r on e ou n ce of a d d i t iv e i n t o t h e

cooling system. The addit ive is available through the

p a r t s d ep a r t m en t . P l a c e t h e h ea t e r con t r ol u n it i n

H E AT p os it i on . S t a r t a n d op er a t e t h e e ng in e u n t il

t h e r a d i a t o r u p p e r h o s e i s w a r m t o t h e t o u c h . A i mt h e com m er ci a l ly a v a i l a b le b la c k l ig h t t ool a t t h e

co m p o n e n t s t o be ch e ck e d . I f le a k s a r e p r e se n t , t h e

b la c k l i gh t w i ll ca u s e t h e a d d i t iv e t o g low a b r ig h t

green color.

T h e bla ck l ig h t ca n be u se d a lo n g w it h a p r e ssu r e

t e st e r t o d e t e r m in e i f a n y e x t e r n a l le a k s e x ist (F ig .

12).

PRESSURE TESTER METHOD

The engine should be at the normal operating tem-

p er a t u r e. R ech eck t h e s y st e m col d i f t h e ca u s e of

coolant loss is not located during warm engine exam-

ination.

WARNING: HOT, PRESSURIZED COOLANT CAN

CAUSE INJURY BY SCALDING.

C a r e f u lly r e m ove t h e r a d ia t o r p r essu r e ca p f r om

t h e f il le r n eck a n d ch eck t h e cool a n t l ev el . P u s h

d ow n on t h e c a p t o d i s en g a g e i t f r om t h e s t o p t a b s .

Wipe t h e in n e r p a r t of t h e f il ler n e ck a n d e xa m in e

the lower inside sealing seat for nicks, cracks, paint ,

dirt a nd solder residue. I nspect t he reserve/overflow

t a n k t u b e f or i n t er n a l ob s t ru ct i on s . I n s e r t a w i r e

t h r ou g h t h e t u be t o be su r e i t is n o t obst r u ct e d .

I n sp ect t h e ca m s on t h e o u t side p a r t of t h e f i l le r

n e c k . I f t h e c a m s a r e b e n t , s e a t i n g o f p r e s s u r e c a p

va lve a n d t e st e r se a l w il l be a f f e ct e d . Re p la ce ca p i f

ca m s a r e be n t .

At t a ch p r essu r e t e st e r 7700 (or a n e q u iva le n t ) t o

the radiator filler neck (Fig. 13).

Operate the tester pump to apply 124 kPa (18 psi)

p r e ssu r e t o t h e sy st e m . I f t h e h o se s e n la r g e e x ce s-

sive ly or bu lg e w h ile t e st in g , r e pla ce a s n e ce ssa r y .

O bse r ve t h e g a u g e p oin t e r a n d d e t er m in e t h e con d i-

tion of the cooling system according to the following

criteria:

H o ld s S t e a d y : I f t h e p o in t e r r e m a in s st e a d y f o r

t w o m i n ut e s, t h e re a r e n o s er i ou s cool a n t l ea k s i n

the system. However, there could be an internal leak

t h a t d o e s n o t a p p e a r w i t h n o r m a l s y s t e m t e s t p r e s -

su r e . I n sp e ct f o r in t e r io r le a k a g e o r d o t h e I n t e r n a lL e a k a g e Te st . D o t h is i f i t is cer t a in t h a t coola n t is

bein g lo st a n d n o le a k s ca n be d e t e ct e d .

D r o p s S lo w ly : S h o w s a sm a ll le a k o r se e p a g e is

occu r r in g. Ex a m in e a l l con n e ct ion s f or se ep a g e or

sl ig h t lea k a g e w it h a f la sh lig h t . I n sp e ct t h e r a d ia t o r,

h o se s, g a sk e t e d g e s a n d h e a t e r . S e a l a n y sm a ll le a k

h oles w it h a S e a le r L u br ica n t or e q u iva le n t . Re pa ir

l ea k h ol es a n d r ei n sp ect t h e s y st e m w i t h p res s u re

applied.

D r o p s Q u ick ly : S h o w s t h a t a se r io u s le a k a g e is

occu r r in g. Ex a m in e t h e sy st e m f or se r iou s e xt e r n a l

Fig. 12 Leak Detection Using Black LightTypical

TYPICAL BLACKLIGHT TOOL

Fig. 13 Pressurizing SystemTypical

TYPICAL COOLING SYTEMPRESSURE TESTER




20/40

lea k a g e . I f n o le a k s a r e visible, in spe ct f or in t er n a l

leakage. Large radiator leak holes should be repaired

by a r e p u t a ble r a d ia t o r r e p a ir sh o p .

INTERNAL LEAKAGE INSPECTION

Re m o ve t h e e n g in e o i l p a n d r a in p lu g a n d d r a in a

sm a ll a m o u n t of e n gin e o il . C oola n t , bein g h e a vier

t h a n e n gin e oi l , w il l d r a in f irst . An ot h e r w a y of t e st -

ing is to operate the engine and check for water glob-

u le s on t h e e ng in e oi l d i ps t i ck . Al so i n sp ect t h e

a u t o m a t ic t r a n sm ission oi l d ip st ick f or w a t e r g lob-

ules. Inspect the automatic transmission fluid cooler

for leakage. Operate the engine without the pressure

ca p o n t h e r a d ia t o r u n t i l t h e r m o st a t o p e n s.

Attach a pressure tester to the filler neck. If pres-

su r e bu ild s u p q u ick ly , a le a k e x ist s a s a r e su lt o f a

f a u lt y cy l in d e r h e a d g a sk e t o r cra ck in t h e e n g in e.

Repair as necessary.

WARNING: DO NOT ALLOW PRESSURE TOEXCEED 124 KPA (18 PSI). TURN THE ENGINE OFF.TO RELEASE THE PRESSURE, ROCK THE TESTERFROM SIDE TO SIDE. WHEN REMOVING THE

TESTER, DO NOT TURN THE TESTER MORE THAN1/2 TURN IF THE SYSTEM IS UNDER PRESSURE.

I f t h e r e is n o im m e d ia t e p r e ssu r e in cr e a se , p u m p

t h e p res s ur e t e st e r u n t il t h e i n di ca t e d p re ss u r e i s

w i t hi n t h e s y st em r a n ge. Vi br a t i on of t h e g a u ge

pointer indicates compression or combustion leakage

into the cooling system.

WARNING: DO NOT DISCONNECT THE SPARK

PLUG WIRES WHILE THE ENGINE IS OPERATING.

CAUTION: Do not operate the engine with a sparkplug shorted for more than a minute. The catalyticconverter may be damaged.

I s ol a t e t h e com p re ss ion l ea k b y s h or t i ng e a ch

spark plug to the cylinder block. The gauge pointer

sh ou ld st op or d e cr e a se vibr a t ion w h e n sp a r k p lu g

for leaking cylinder is s horted. This happens because

of the absence of combustion pressure.

COMBUSTION LEAKAGE TEST (WITHOUTPRESSURE TESTER)

DO NOT WASTE reusable coolan t . I f the solution

is cle a n , d r a in t h e co o la n t in t o a cle a n co n t a in e r f o r

reuse.

WARNING: DO NOT REMOVE THE CYLINDER

BLOCK DRAIN PLUGS OR LOOSEN THE RADIATORDRAINCOCK WITH THE SYSTEM HOT AND UNDERPRESSURE. SERIOUS BURNS FROM COOLANTCAN OCCUR.

D r a i n s u ff ici en t cool a n t t o a l l ow f or t h e rm os t a t

removal. Refer to Thermosta t Replacement. Discon-

n e ct t h e w a t e r p u m p d r ive be lt .

D iscon n e ct t h e u p pe r r a d ia t o r h ose f r o m t h e t h e r -

mostat housing. Remove the housing and thermostat .

I n st a l l t h e t h e r m o st a t h o u sin g .

Ad d cool a n t t o t h e r a d i a t or t o b r i n g t h e l ev el t ow it h in 6.3 m m (1/4 in ) of t h e t o p o f t h e t h e r m ost a t

housing.

CAUTION: Avoid overheating. Do not operate theengine for an excessive period of time. Open the

draincock immediately after the test to eliminateboil over of coolant.

S t a r t t h e e n g in e a n d a cce le r a t e r a p id ly t h r e e t im e s

(t o a p pr ox im a t e ly 3000 r pm ) w h i le ob s er v in g t h e

coolant . I f internal engine combustion gases are leak-

in g in t o t h e co o lin g sy st e m , bu bble s w il l a p p e a r in

t h e cool a n t . I f b u bb le s d o n o t a p pe a r, t h e re i s n ointernal combustion gas leakage.

VISCOUS FAN DRIVE

LEAKS

Viscous fan drive operation is not affected by small

o i l s t a in s n e a r t h e d r ive be a r in g . I f le a k a g e a p p e a r s

excessive, replace the fan drive unit .

TESTING

I f t h e f a n a sse m bly f r ee -w h e els w it h ou t d r a g (t h e

f a n b la d e s w i ll r ev ol ve m or e t h a n f iv e t u r n s w h e n

sp u n by h a n d ), r e p la ce t h e f a n d r ive . T h is sp in t e st

must be performed when the engine is cool.

F o r t h e f ol low in g t e st , t h e coolin g sy st e m m u st be

in g ood con d it ion . I t a lso w il l e n su r e a g a in st e xce s-

sively high coolant temperature.

WARNING: BE SURE THAT THERE IS ADEQUATEFAN BLADE CLEARANCE BEFORE DRILLING.

(1) Dr ill a 3.18-mm (1/8-in) dia meter hole in the

t o p cen t e r of t h e f a n sh r ou d .

(2) O bt a in a d ia l t h e r m om e t er w it h a n 8 in ch st e m

(or e q u iva le n t ). I t sh ou ld h a ve a r a n g e of -18 -t o -

105C (0-to-220 F). Insert thermometer through the

h ol e i n t h e s h r ou d . B e s u r e t h a t t h e re i s a d e q ua t e

cle a r a n ce f r om t h e f a n bla d es.

(3) C o n n ect a t a ch om e t er a n d a n e n gin e ig n it ion

t i m in g l ig h t (t i m in g l ig h t i s t o b e u s ed a s a s t r ob e

light).

(4) Block the air f low through the radiator. Secure

a sh e et of p la st ic in f r on t of t h e r a d ia t o r (or a ir con -

dit ioner condenser). Use tape at the top to secure the

p la st ic a n d be su r e t h a t t h e a ir f lo w is blo ck e d .

(5) B e sure t ha t the a ir conditioner (if equipped) is

turned off .




21/40

WARNING: USE EXTREME CAUTION WHEN THEENGINE IS OPERATING. DO NOT STAND IN ADIRECT LINE WITH THE FAN. DO NOT PUT YOURHANDS NEAR THE PULLEYS, BELTS OR FAN. DONOT WEAR LOOSE CLOTHING.

(6) S t a r t t h e en g in e a n d oper a t e a t 2400 r pm .

Within ten minutes the air temperature (indicated on

the dia l th ermometer) should be up to 88 C (190 F).

F a n d r iv e engagement should have started to occura t b et w e en 74 t o 8 2 C (165 t o 1 80 F ). E n g a g e-

ment is dist inguishable by a definite increase i n f a nflow noise (roaring). The t iming light also w ill indi-

ca t e a n in cr e a se in t h e sp e e d o f t h e f a n .

(7) When t he a ir t empera ture rea ches 88 C (190

F ), r e m o ve t h e p la st ic sh e e t . F a n d r ive disengage-ment sh ou ld h a ve st a r t e d t o o ccur a t bet w e e n 57 t o79 C (135 t o 175 F ). A d e f in it e decrease o f f a nflow noise (roaring) should be noticed. If not , replace

the defective viscous fan drive unit .

AUXILIARY ELECTRIC COOLING FAN

ELECTRIC COOLING FAN AND RELAY

DIAGNOSIS

NOTE: Refer to Electrical Group 8W for electriccooling fan and relay circuit schematic.

The powertrain control module (PCM) will enter a

diagnostic t rouble code (DTC) in memory if it detects

a problem in the a uxiliary cooling fan relay or circuit .

Refer to G roup 25, Em ission Control Syst ems for cor-

rect DTC retrieval procedures.

If the electric cooling fa n is inoperat ive, check fuse

#11 (20A) in junction block and fuse #5 (40A maxi-

f u se ) in t h e Po w e r D ist r ibu t io n C e n t e r (PD C ) w it h a

12 volt test lamp or DVOM. If fuses are o.k., refer to

G r o u p 8W for e le ct r ic coolin g f a n a n d r e la y cir cuit

schematic.

RADIATOR CAP-TO-FILLER NECK SEALPRESSURE RELIEF CHECK

With rad iator cap insta lled on filler neck, remove

coolant reserve/ overflow ta nk hose from nipple on

f i ller n e ck . C o n n e ct a h a n d op er a t e d va cu u m p u m pto nipple. Operat e pump until a reading of 47-to-61

kPa (14- to-18 in. Hg) appears on gauge. If the read-

in g st a y s st e a d y , o r d r o p s sl ig h t ly a n d t h e n r e m a in s

steady, the pressure valve seal is good. Replace radi-

a t o r ca p i f r e a d in g d o e s n o t h o ld .

WARNING: THE WARNING WORDS -DO NOT OPENHOT- ON THE RADIATOR PRESSURE CAP (Fig. 14)ARE A SAFETY PRECAUTION. WHEN HOT, PRES-

SURE BUILDS UP IN COOLING SYSTEM. TO PRE-VENT SCALDING OR INJURY, THE RADIATOR CAP

SHOULD NOT BE REMOVED WHILE THE SYSTEM

IS HOT AND/OR UNDER PRESSURE.

Th er e is n o n eed t o r em ov e t h e r a dia t or ca pexcept for the following purposes:

(1) To check and adjust an tifreeze freeze point .

(2) To refill syst em w ith new an tifreeze.

(3) For conducting service procedures.

(4) When checking for vacuum leaks.

WARNING: IF VEHICLE HAS BEEN RUNRECENTLY, WAIT AT LEAST 15 MINUTES BEFOREREMOVING RADIATOR CAP. WITH A RAG,

SQUEEZE RADIATOR UPPER HOSE TO CHECK IFSYSTEM IS UNDER PRESSURE. PLACE A RAGOVER THE CAP AND WITHOUT PUSHING DOWN,

ROTATE CAP COUNTER-CLOCKWISE TO THEFIRST STOP. ALLOW FLUID TO ESCAPE THROUGHOVERFLOW HOSE INTO COOLANT RESERVE/OVERFLOW TANK. SQUEEZE RADIATOR UPPERHOSE TO DETERMINE WHEN PRESSURE HASBEEN RELEASED. WHEN COOLANT AND STEAM

STOP BEING PUSHED INTO TANK AND SYSTEMPRESSURE DROPS, REMOVE RADIATOR CAPCOMPLETELY.

Fig. 14 Radiator Pressure Cap

PRESSURE RATINGFILLER NECK SEALPRESSURE VALVEVACUUM VENT VALVE (SHOWN IN SEAL-ING POSITION)




22/40

PRESSURE TESTING RADIATOR CAPSR em ov e c a p f r om r a d i a t or. B e s u r e t h a t s ea l i ng

su r f a ce s a r e clea n . Moist en r u bbe r g a sk e t w it h w a t e r

a n d in st a l l t h e ca p o n p r e ssu r e t e st e r ( t o o l 7700 o r

an equivalent) (Fig. 15).

O pe ra t e t h e t e st e r p um p a n d ob s er v e t h e g a u g e

pointer at its highest point . The cap release pressure

should be 83-to-110 kP a (12-to-16 psi). The ca p is sa t-isfa ct or y w h e n t h e p r e ssur e h o ld s st e a d y. I t is a lso

g ood i f i t h old s p r essu r e w it h in t h e 83-t o -110 k P a

(12-to-16 psi) ra nge for 30 seconds or more. If the

pointer drops quickly, replace the cap.

CAUTION: Radiator pressure testing tools are very

sensitive to small air leaks, which will not causecooling system problems. A pressure cap that doesnot have a history of coolant loss should not bereplaced just because it leaks slowly when testedwith this tool. Add water to tool. Turn tool upside

down and recheck pressure cap to confirm that cap

needs replacement.

CAP INSPECTIONVisu a lly in spe ct t h e p r essu r e va lve g a sk e t on t h e

ca p . R ep la c e c a p i f t h e g a s k et i s s w ol le n, t or n or

worn. Inspect the area around radiator filler neck for

w h it e d e p o sit s t h a t in d ica t e a le a k in g ca p .

LOW COOLANT LEVEL-AERATIONI f t h e coola n t level in r a d ia t or d r op s be low t o p o f

radiator core tubes, air will enter cooling system.

Low coolant level can cause thermostat pellet to be

su sp e n d e d in a ir in st e a d o f co o la n t . T h is w il l ca u se

thermostat to open later, which in turn causes higher

coola n t t e m pe r a t u r e . Air t r a p pe d in coolin g sy st em

a lso r e d u ce s a m o u n t of coola n t cir cu la t in g in h e a t e r

core result ing in low heat output.

DEAERATIONAs the engine operates, any air trapped in cooling

system gathers under the radiator cap. The next t ime

the engine is operated, thermal expansion of coolant

w i l l p us h a n y t r a p pe d a i r p a s t r a d i a t or ca p i n t o t h e

coolan t reserve/overflow ta nk. Here it escapes to the

a t m o sp he re i n t o t h e t a n k . Wh en t h e en g in e cool s

d o w n t h e co o la n t , i t w il l be d r a w n f r o m t h e r e se r ve /

ov er flow t a n k in t o t h e r a dia t or t o r epla ce a n y

removed air.

SERVICE PROCEDURES

COOLANT LEVEL CHECK ROUTINE

NOTE: Do not remove radiator cap for routinecoolant level inspections. The coolant level can bechecked at coolant reserve/overflow tank.

The coolant reserve/overflow system provides a

q u ick visu a l m e t h od f or d e t er m in in g coola n t level

without removing radiator pressure cap. With engine

col d a n d n ot r u nn in g, ob ser ve cool a n t l ev el i n

reserve/overflow ta nk. The coolan t level should be

be t w e e n AD D a n d F U L L m a r k s.

COOLANT SERVICEI t i s r ecom m en d ed t h a t t h e cool in g s ys t em b e

d r a in e d a n d f lu sh ed a t 84,000 k ilom e t er s (52,500

miles), or 3 years, whichever occurs first. Then every

t w o y ea r s , or 48, 000 k il om et e rs (30, 000 m i le s),

wh ichever occurs first .

ADDING ADDITIONAL COOLANT ROUTINEDo not remove radiator cap to add coolant to

system. Wh e n a d d in g coola n t t o m a in t a in cor r e ctlevel, do so a t coolant reserve/overflow ta nk. Use a

50/50 mixtu re of eth ylene-glycol a ntifreeze conta iningAluga rd 340-2 a n d l ow m i n er a l con t en t w a t e r.

Re m o ve r a d ia t o r ca p o n ly f o r t e st in g o r w h e n r e f i l l-

ing system after service. Removing cap unnecessarily

ca n ca u se lo ss o f co o la n t a n d a l lo w a ir t o e n t e r sy s-

tem, which produces corrosion.

COOLANT LEVEL CHECK SERVICEThe cooling syst em is closed a nd designed to m ain-

tain coolant level to top of radiator.

Fig. 15 Pressure Testing Radiator PressureCapTypical




23/40

WARNING: DO NOT OPEN RADIATOR DRAINCOCKWITH ENGINE RUNNING OR WHILE ENGINE IS HOTAND COOLING SYSTEM IS UNDER PRESSURE.

Wh e n ve h icle se r vicin g r e q u ir e s a coola n t level

ch eck i n r a d i a t or, d r a i n s ev er a l ou n ce s of cool a n t

f r om r a d i a t or d r a i n cock . D o t h i s w h i le ob s er v in g

coolant reserve/overflow system ta nk. The coolan t

level in r eserve/overflow ta nk should d rop slightly. If

n ot , in spe ct f or a lea k bet w e e n r a d ia t o r a n d coola n t

reserve/overflow syst em connection. R emove ra dia tor

cap. The coolant level should be to top of radiator. I f

not a nd if coolan t level in reserve/overflow t an k is at

ADD mark, check for:

An air leak in coolant reserve/overflow ta nk or

its hose

An a ir le a k in r a d ia t o r f i l le r n e ck

L e a k in p r essu r e ca p se a l t o r a d ia t o r f i l le r n e ck

DRAINING AND FILLING COOLING SYSTEMDRAINING 2.5L 4-CYLINDER ENGINE

WARNING: DO NOT REMOVE THE CYLINDER BLOCK

DRAIN PLUGS OR LOOSEN THE RADIATOR DRAIN-

COCK WITH SYSTEM HOT AND UNDER PRESSURE.

SERIOUS BURNS FROM COOLANT CAN OCCUR.



reuse.

D O N OT r em ov e t h e r a d i a t or ca p w h e n d r a i n in g

th e coolant from th e reserve/overflow t a nk. Open t he

r a d ia t or d r a in cock a n d w h en t h e t a n k i s em pt y,

r e m ove t h e r a d ia t or ca p . Th e coola n t d oe s n o t h a ve

t o b e r em ov ed f r om t h e t a n k u n le ss t h e s y s t e m i s

being refilled with a fresh mixture.

(1) D r a in t h e co o la n t f r o m t h e r a d ia t o r by lo o se n -

ing the petcock.

(2) D r a in coola n t f r om e n g in e by r e m ovin g d r a in

plug at left rear side of block.

DRAINING 4.0L 6-CYLINDER ENGINE

WARNING: DO NOT REMOVE THE CYLINDER BLOCK

DRAIN PLUGS OR LOOSEN THE RADIATOR DRAIN-

COCK WITH SYSTEM HOT AND UNDER PRESSURE.

SERIOUS BURNS FROM COOLANT CAN OCCUR.



reuse.

(1) Remove radiator pressure cap.

(2) F or a c ces s t o r a d i a t or d r a i n cock (F i g. 16),

r e m o ve r a d ia t o r g r i l le m o u n t in g scr e w s a n d r e m o ve

grill . Refer to Group 23, Body for correct procedure.

(3) Atta ch one end of a 24 inch long X 1/4 inch I D

hose to the radiator draincock. Put the other end into

a clean container. Open draincock and drain coolant

from radiator.

(4) D r a i n cool a n t f r om en g in e b y r em ov in g t h e

d r a i n p lu g a n d cool a n t t e m per a t u r e s en s or on l ef t

side of block.

REFILLING COOLING SYSTEM

(1) Tig h t en t h e r a d ia t o r p et cock a n d t h e cyl in d e r

block dra in plug(s). I f r emoved, insta ll coolan t tem-

perature sensor (4.0L 6-cylinder engine).

(2) Fill system using a 50/50 mixture of w at er a nd

antifreeze as described in the Coolant section of this

g r o u p . F i l l r a d i a t o r t o t o p a n d i n s t a l l r a d i a t o r c a p .

Ad d su f ficien t coola n t t o r e se r ve /over f low t a n k t o

r a ise le ve l t o F U L L m a r k .

(3) With heater control unit in the HE AT posit ion,

o p e r a t e e n g in e w it h r a d ia t o r ca p in p la ce .

(4) Af t er en g in e h a s r ea c h ed n or m a l op er a t i n g

t e m pe r a t u r e , sh u t e n gin e o ff a n d a l low i t t o cool .

(5) Add coolan t to r eserve/overflow ta nk a s neces-

sary. Only add coolant when the engine is cold.Coolant level in a warm engine will be higherdue to thermal expansion.

REVERSE FLUSHINGCAUTION: The cooling system normally operates

at 97-to-124 kPa (14- to-18 psi) pressure. Exceedingthis pressure may damage the radiator or hoses.

Reverse flushing of the cooling system is the forc-

ing of water through the cooling system. This is done

using a ir pressure in the opposite direction of normal

coola n t f low . I t is u su a lly on ly n e cessa r y w it h ver y

d ir t y sy st e m s w it h e vid en ce of p a r t ia l p lu g g in g .

Fig. 16 Radiator Petcock4.0L (LHD/RHD)

RADIATOR PETCOCK


SERVICE PROCEDURES (Continued)


24/40

CHEMICAL CLEANING

If visua l inspection indicat es th e formation of sludge or

s ca l y d e pos i t s , u s e a r a d i a t o r cl ea n e r (Mop a r R a d i a t o r

K l ee n or e q u iv a l en t ) b ef or e f lu s h in g . Th i s w i l l s of t e n

scale and other deposits and aid the f lushing operation.

CAUTION: Be sure instructions on the containerare followed.

REVERSE FLUSHING RADIATOR

Disconnect the radiator hoses from the radiator fit-

t in g s. At t a ch a se ct io n o f r a d ia t o r h o se t o t h e r a d ia -

t o r bo t t o m o u t le t f i t t in g a n d in se r t t h e f lu sh in g g u n .

C o n n e ct a w a t e r su p p ly h o se a n d a ir su p p ly h o se t o

t h e f lush in g g u n .

CAUTION: The cooling system normally operatesat 97-to-124 kPa (14- to-18 psi) pressure. Exceedingthis pressure may damage the radiator or hoses.

Allow the radiator to fill with water. When radiator

is f i lled , a p ply a ir in sh or t bla st s a l low in g r a d ia t o r t o

r e fi ll bet w e e n bla st s . C on t in u e t h is r e ve r se f lu sh in g

u n t i l c le a n w a t e r f lo w s o u t t h r o u g h r e a r o f r a d ia t o r

cooling tube passages. For more information, refer to

operating instructions supplied wit h flushing equip-

m e n t . H a ve r a d ia t or cle a n e d m o r e e xt e n sively by a

radiator repair shop.

REVERSE FLUSHING ENGINE

D r a in t h e co o lin g sy st e m . Re m o ve t h e t h e r m o st a t

h ou sin g a n d t h e r m ost a t . I n st a l l t h e t h e r m ost a t h ou s-

i n g. D i s con n ect t h e r a d i a t or u pp er h os e f r om t h er a d ia t or a n d a t t a ch t h e f lu sh in g g u n t o t h e h ose . D is-

con n ect t h e r a d ia t or l ow e r h os e f rom t h e w a t e r

p um p . At t a c h a l ea d a w a y h os e t o t h e w a t e r p u m p

inlet f it t ing.

CAUTION: Be sure that the heater control valve isclosed (heat off). This is done to prevent coolantflow with scale and other deposits from entering

the heater core.

Connect the water supply hose and air supply hose

t o t h e f lu s hi n g g u n. Al low t h e e ng in e t o f il l w i t h

w a t e r . W h e n t h e e n g in e is f i l le d , a p p ly a ir in sh o r tbla st s , a l lo w in g t h e sy st e m t o f i l l be t w e e n a ir bla st s .

C on t i n ue u n t il cl ea n w a t er f low s t h r ou g h t h e l ea d

a w a y h o se . F o r m o r e in f o r m a t io n , r e f e r t o o p e r a t in g

instructions supplied with flushing equipment.

R e m o v e the l e a d a w a y ho s e , f l us hi ng g un, w a te r s up-

pl y ho s e a nd a i r s uppl y ho s e . R e m o v e the the r m o s ta t

h o u s i n g a n d i n s t a l l t h e r m o s t a t . I n s t a l l t h e t h e r m o s t a t

housing with a replacement gasket. Refer to Thermostat

R ep la c em en t . C on n ect t h e r a d i a t or h os es . R ef il l t h e

cool ing s y s tem w i th the cor r e ct a nt i f r ee ze /w a te r m i x-

tur e .

REMOVAL AND INSTALLATION

TRANSMISSION OIL COOLERS

WATER-TO-OIL COOLER

The internal transmission oil cooler located within

the radiator is not serviceable. If it requires service,t h e r a d ia t o r m u st be r e p la ce d .

Onc e the r e pa i r e d o r r e pl a c e m e nt r a d i a to r ha s b e e n

i ns ta l l ed , f i ll the cool ing s y s tem a nd i ns pe ct f or l ea k s .

Refer to t he Refil l ing Cooling S ystem an d Testing C ool-

i n g S y s t e m F or L ea k s s ect i on s i n t h i s g r ou p. I f t h e

transmission operates properly af ter repairing the leak,

d r a i n the t r a ns m i s s ion a nd r e m ov e the t r a ns m i ss i on oi l

pan. Inspect for s ludge a nd/or rust. Inspect for a dirty

or plug g ed i nl et f i lte r. I f no

EXJ_799 jeep xj service manual

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