ASE A1 Engine Repair Practice Test

1. A vehicle has heavy white smoke emitting from its tailpipe at all engine speeds. The cause of this problem is: A. Worn piston rings. B. A leaking head gasket. C. Worn valve seals. D. A leaking fuel injector.

2. A vacuum gauge is connected to a port on the intake manifold of an engine with poor performance. The needle on the gauge fluctuates between 15 "hg and 20 "hg vacuum at idle. This vacuum gauge reading indicates: A. A normal condition. B. Late ignition or valve timing. C. A sticking valve or misfire. D. A restricted exhaust system.

3. Technician A says an engine's main bearing insert has a hole that must align with the matching bores oil supply hole. Technician B says that crankshaft bore alignment can be checked with a feeler gauge and a straightedge. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

4. A cylinder power balance test is being performed on a vehicle with sequential fuel injection. Two adjacent cylinders are under performing. Technician A says this could be due to a faulty head gasket. Technician B says this could be due to leaking secondary insulation. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B5. Two technicians are discussing hydraulic lifter preload. Technician A says excessive preload will cause high manifold vacuum. Technician B says insufficient preload will cause excessive valve train noise. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

6. Technician A says the valves in many interference engines open further into the combustion chamber that than those of a non-interference engine. Technician B says a broken timing belt in an interference engine can result in damage to the engine's valve train. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

7. The spark plug is removed and shop air is introduced to the #1 cylinder while at TDC. Bubbles are seen in the radiator neck. The MOST likely cause of this condition is: A. A bent intake valve. B. Worn piston rings. C. A burned exhaust valve. D. A leaking head gasket.8. The torque converter of an automatic transmission is not engaging. This is resulting in poor fuel mileage. Technician A says the ECT sensor's signal will affect TCC application. Technician B says the ECT sensor will affect the engine's fuel mixture. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B9. Technician A says a flex fan will increase its pitch at higher engine speeds. Technician B says a viscous fan clutch contains a silicon based fluid and should be checked for leaks. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

10. A vehicle has a clogged catalytic converter. The LEAST likely cause of this is: A. A rich fuel condition. B. A leaking fuel injector. C. A cracked intake manifold. D. A fouled spark plug.

11. After diagnosing and replacing the cooling system's water pump, the vehicle's engine continues to overheat. Which of these is the MOST likely cause. A. An air pocket in the system. B. Leaking head gasket. C. Faulty replacement water pump. D. The radiator.

12. Two technicians are discussing engine sealants and form in place gaskets. Technician A says sealants such as RTV are aerobic. Technician B says some sensors may be damaged if an unapproved sealant is used. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

13. An engine has a noise that goes away as the engine warms and reaches operating temperature. Which of these is the MOST likely cause. A. Loose main bolt. B. Loose connecting rod bolt. C. Piston to wall clearance. D. Loose intake manifold.14. An engine suffers from detonation. Technician A this may be caused from a defective EGR valve. Technician B says advanced ignition timing can cause this condition. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B15. Technician A says faulty turbocharger bearings will result in a loss of engine oil. Technician B says a dirty turbocharger air filter will result in a loss of engine oil. Who is correct?A. Technician A B. Technician B C. Both A and B D. Neither A or B

16. A squeal is heard in the front of a supercharged V6 engine. This squeal gets louder as the engine is accelerated. Which of these is causing this condition? A. Supercharger front roller bearings. B. Faulty serpentine belt tensioner. C. Turbine shaft needle bearings. D. Both A or B17. A vehicle's engine is sluggish and slow to crank. Technician A says to check the starter and its circuit first. Technician B says to check the voltage, capacity, and condition of the battery. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

18. A vehicle vibrates only when placed in reverse. The MOST likely cause of this condition is: A. Crossed ignition wires. B. A faulty fuel injector. C. A out of balance balance shaft. D. A broken engine mount.

19. Two technicians are discussing cylinder bore measurements. Technician A says the cylinder's bore should be measured for out of round. Technician B says the cylinder's bore should be measured and checked for taper. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B20. Technician A says that connecting rods and the rod caps are matched and can not be mixed. Technician B says it may be necessary to mark these parts for reassembly. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

21. Engine crack repair is being discussed. Technician A says metal pinning is an accepted method of cracked cylinder head repair. Technician B says metal pinning is an accepted method of cracked engine block repair. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

22. Which of these is LEAST likely to cause low oil pressure in an engine. A. A faulty oil pressure valve. B. A worn crankshaft bearings. C. A worn camshaft bearings. D. A worn valve guides.

23. Technician A says valve spring installed height is measured from the outer edge of the valve spring retainer to the pocket in the cylinder head. Technician B says that too thin of a valve margin will not effect its operating temperature. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

24. Technician A says that magnetic particle detection is an acceptable method to detect cracks in aluminum castings. Technician B says a special dye is used to detect cracks in aluminum castings. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

25. Technician A says that minor scoring on the surface of a flywheel can be removed. Technician B says if the ring gear on an automatic transmission's flexplate shows excessive wear and slight cracking it must be replaced. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

26. Two technicians are discussing the camshaft in a V8 engine. Technician A says to use an outside micrometer to measure the diameter of a camshaft journal. Technician B says a camshaft spins twice for every one revolution of the crankshaft. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

27. A vehicle is emitting black exhaust from its tailpipe under all driving conditions. This is because:

A. There is oil in the combustion chamber. B. There is coolant in the combustion chamber. C. There is too much fuel in the combustion chamber. D. There is too much air in the combustion chamber.28. The top compression ring groove of piston is worn excessively and the gap is found to be larger than specifications. The technician would MOST likely:

A. Use a tapered ring set to repair this piston. B. Use oversized rings to repair this piston. C. Use a ring groove cleaner to repair the grooves. D. Replace the piston.29. A strong sulfur smell is coming from the tailpipe of a vehicle. The MOST likely cause of this condition is: A. A lean fuel condition. B. Leaking head gasket. C. Worn piston rings. D. A rich fuel condition.

30. A technician performs a battery capacity test on a vehicle that will not start. The test results in a reading of 9.1 volts at 70 F. Technician A says the battery has failed the capacity test. Technician B says battery voltage readings will increase as temperature decreases. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

31. After performing a cylinder pressure test on a four cylinder engine. The #1 cylinder is found to be 30 psi below specifications. All the other cylinders have passed. The pressure in the #1 cylinder increased after injecting engine oil. Technician A says excessive carbon buildup has caused of these test results. Technician B says these results indicate a faulty engine valve. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

32. One valve tip on a cylinder head is much higher than the others. The MOST likely cause of this is: A. Weak spring tension. B. Valve spring installed height. C. The valve face. D. Loose head bolts.

33. Two technicians are discussing a ballooned oil filter. WhIch of these is causing this condition: A. Contaminated oil. B. Stuck closed oil pressure relief valve. C. Stuck closed oil filter bypass valve. D. All of the above.

34. Technician A says that torque to yield bolts can always be reused. Technician B says that torque to yield bolts can be reused as long as they are cleaned and oiled before they are reinstalled and torqued. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

35. The best tool for checking crankshaft end play is a: A. Bore gauge. B. Digital micrometer. C. Dial indicator. D. None of the above.

36. A vehicle's cooling system is loosing coolant. There is corrosion found around the aluminum water pump. Which of these is MOST likely to cause this condition. A. Stuck open thermostat. B. Electrolysis. C. Loose radiator cap. D. Faulty head gasket.

37. A technician installs a radiator pressure tester on the radiator of a cold engine. After starting the engine the pressure quickly rises to 18 psi. Technician A says this is a normal condition. Technician B says the engine has a leaking cylinder head gasket. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

38. Two Technicians are discussing a PCV system. Technician A says a stuck closed PCV valve could cause external oil leaks. Technician B says that the PCV system removes blowby gases from the engine case. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

39. An OHC engine has recently had the cylinder head replaced. The engine runs rough and stumbles. Technician A says this may be caused by incorrect valve lash adjustment. Technician B says that only in-block camshafts require valve lash adjustments. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B40. Technician A says worn valve springs result in valve float at wide open throttle. Technician B says valve springs should be inspected for squareness with a square and a feeler gauge. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

41. A wet compression test is being performed on a four cylinder engine. The number two cylinder's compression is below specifications and remains the same after injecting oil. This result indicates: A. Worn piston rings. B. A faulty valve. C. A hole in the piston. D. Excessive carbon buildup on the piston's dome.

42. A metallic knocking sound is heard behind an engine's harmonic balancer. An oil pressure test indicates oil pressure is below specifications. Technician A says the engine's main bearing inserts should be inspected for wear. Technician B says a worn thin crankshaft thrust bearing will cause this condition. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

43. Technician A says to remove the ridge on the engine block before removing the pistons. Technician B says a block's ridge will damage the new piston rings during installation. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

44. A vehicle briefly blows blue/gray smoke from the tailpipe when it's first started in the morning. The MOST likely cause of this condition is: A. Worn piston rings. B. Lean fuel condition. C. Leaking fuel injector. D. Leaking valve seal.

45. During a cylinder leakage test air bubbles appear in the neck of the radiator. Technician A says a faulty intake valve will cause this condition. Technician B says a crack in the engine block will cause this condition. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

46.

The reading on the micrometer indicates: A. 6.05 mm B. 6.00 mm C. 5.50 mm D. 6.50 mm

47. A technician is checking for piston ring groove clearance. The proper technique includes. A. The old ring and a feeler gauge. B. The new ring and a feeler gauge. C. Only a feeler gauge. D. No feeler gauge is required.

48. A cylinder power balance test is being performed on a vehicle with sequential fuel injection. The number five cylinder's rpm drop is less than all of the others. Technician A says this could be the result of a restriction in the fuel injector. Technician B says this could be caused by leaking secondary insulation. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

49. Two technicians are discussing a turbocharged engine. Technician A says the wastegate is a component used to control boost pressure. Technician B says when opened, the wastegate diverts exhaust gas from the turbine wheel. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

50. Technician A says a supercharger uses an intercooler to keep the engine's oil cool. Technician B says intercoolers are used on turbochargers to keep the oil cool. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B

Answers1. B 2. C3. C4. C5. B6. C7. D8. C9. B10. C11. A12. C13. C14. C15. A16. D17. B18. D19. C20. C21. C22. D23. A24. B25. C26. A27. C28. D29. D30. A31. D32. C33. D34. D35. C36. B37. B38. C39. A40. C41. B42. C43. C44. D45. B46. D47. B48. C49. C50. D

EXPLANATION

1. Blue/Gray Smoke: Blue/gray exhaust smoke is an indication of oil burning in the combustion chamber. These are possible symptoms and causes:Valve Seals: Leaking valve seals will cause blue/gray exhaust smoke.Valve Guides: Excessive clearance between the valve stem and the valve guide allows oil to leak past the gap into the cylinder.Piston Rings: Worn or damaged piston rings will cause blow-by, resulting in blue/gray smoke.

Worn Cylinder Walls: Worn cylinder walls cause blow-by, resulting in blue/gray smoke.PCV System: A stuck closed PCV valve causes excessive crankcase pressure, resulting in blue/gray smoke.Black Smoke: Black exhaust smoke is an indication of a rich fuel condition. These are possible causes:Fuel Injectors: A leaking or dripping fuel injector will cause a rich fuel condition.Fuel Pressure Regulator: A stuck closed fuel pressure regulator will cause a rich fuel condition.Fuel Return: A restricted fuel return line will cause a rich fuel condition.White/Gray Smoke: White exhaust smoke is an indication that coolant is burning in the combustion chamber. These are possible causes:Cylinder Head: A crack in the cylinder head (around the coolant jacket) will cause coolant to enter the combustion chamber.Engine Block: A crack in the deck of an engine block near the coolant jacket will cause coolant to enter the combustion chamber.Head Gasket: A damaged or blown head gasket will cause coolant to enter the combustion chamber resulting in white/gray smoke coming from the tailpipe.

2- To check manifold pressure with a vacuum gauge you need to locate a port on the intake manifold or throttle body. Manufacturer's install ports on their manifolds for lots of different reasons: Brake Booster, PCV tube, EGR Switch, A/C vents, etc. You simply need to find one small enough for the vacuum gauge line to slide onto firmly.

A quick snap of the throttle plate should drop the vacuum to around 5 "hg vacuum, and then it should recover to a steady 21 "hg vacuum. When this air is mixed with atomized fuel from the fuel injectors, engine speed is increased. For every 1000 ft. of increase in altitude, 1 "hg is subtracted from the vacuum reading.

Normal Engine: On a normal engine, accelerate to around 2000 rpm and then quickly release the throttle. The engine should snap right back to a steady 17- 21 "hg vacuum.

Steady low between 5-10 "hg vacuum: This indicates that the engine has a leak in the intake manifold or the intake gasket. This leak should be easy to find because it would be making a loud hissing noise.

Steady low between 10-15 "hg vacuum: This reading indicates late valve timing. There's a good chance the vehicle has jumped timing. Check the timing belt or chain depending on the application.

Steady low between 15-18 "hg vacuum: This just low reading indicates retarded ignition timing. Advance the timing on the distributor to correct this problem.

Fluctuating Needle: A fluctuating needle indicates there's a problem with a valve or a there's an engine misfire.

Needle drops during acceleration: If the needle drops steady during acceleration there's a restriction in the exhaust or intake. This is typically due to a clogged CAT or muffler.

3-Crankshaft bearings are made of a softer material than the crankshaft journal or cap they sit in. This insures that the bearing material wears before the journal. The crankshafts journal doesn't actually ride on the bearing surface, instead it rides on a thin film of oil between the journal and the bearings.

If the crankshaft journals are worn, scored, or out of round, the gap between the two are affected. Whenever there is contact between the journal and the bearing there will be excessive wear.

Check the bearing for metal particles embedded into its surface. This indicates that two metal parts are in contact with each other creating metal shavings. It's important to find and repair this problem before proceeding. Whenever you find metal shavings in the oil pan or bearings, the oil pump must also be inspected. Look at the backside of the bearing insert for wear indicting that it has spun in its saddle.

Check the main bearing bore for misalignment. There are several methods to do so. Its easiest to use a straight edge and a feeler gauge. Use a blade half the thickness of the maximum clearance. The feeler gauge must not fit between the straightedge and the bores surface. Warpage can be corrected when it isn't too far out of specifications. The block can be line bored and oversized bearings installed.

4-A cylinder power balance test tests each cylinders effectiveness compared to the others. A weak cylinder could be caused an ignition, fuel delivery, or mechanical problem, such as a faulty valve or worn piston rings. As this question suggests, there may be one or more cylinder involved. A faulty head gasket, cracked cylinder head or block will cause an RPM drop on adjacent cylinders.

For many years, removing a plug boot from its plug was standard procedure. A prolonged open in the secondary ignition system may cause damage to the coil or ignition module. Sometimes a sensor, like an O2 sensor will need to be disconnected so the computer will not try to compensate for the sudden change in conditions. Check with manufacturers specifications before proceeding and remember safety first. Use a grabber or a tool that will protect your hand from any shock that may result from removing the plug cover.

Notice the RPM drop as power is removed from the cylinder. If a cylinder's RPM drop is not consistent with the others, this indicates a problem with that cylinder. An engine analyzer tests each cylinder and then compares the results. It's easy to do the same on a piece of paper. An engine analyzer or dedicated tool is best for testing coil on plug COP ignition systems. This is because coil damage may result from removing a coil pack while the engine is running. Check with the manual, there are many ways to cancel a COP cylinder such as disconnecting the associated connector.

5-To understand hydraulic lifter preload, a comparison could be made between a solid lifter and a hydraulic lifter. Manufacturers specifications are required to set the gap on either of these lifters. A feeler gauge is used to measure the gap between the valve tip and the rocker of a solid lifter. This gap is necessary to accommodate heat expansion in the valve train. Adjusting hydraulic lifters is different. With a hydraulic lifter, the gap is set to zero lash, and then the preload is set. This initial zero lash adjustment is why these lifters have a quieter operation.

This is accomplished with the use of a spring loaded plunger mechanism inside the lifter body. When preload is being set, the plunger is being pushed into the body. Excessive valve train noise will result from insufficient preload. Low manifold vacuum or a rough idle will result from excessive preload. A sticking plunger, like the one shown in the diagram, will likely result in a burned exhaust valve or an intake valve that does not completely close. A sticking open intake valve will cause compression to backfire into the intake manifold.

Adjusting Hydraulic Lifters:

1. To set the lifter preload, turn the engine in its normal rotation until the exhaust lifter just starts to travel upwards.

2. Adjust the intake valve to zero lash and then turn the rocker arm adjustment nut 1/2 to 1 turn. When unsure about something, always use manufacturers specifications. This additional turning of the adjustment nut sets the lifter preload.

3. Rotate the engine until the intake lifter travels all the way up and then almost all the way down.

4. Now set the exhaust valve to zero lash and then turn the rocker arm adjustment nut 1/2 to 1 turn.

6- Interference engines offer a little more performance in their high compression small displacement design. With an interference engine, the valve opens further into the combustion chamber than a non-interference engine. This is great for engine performance because this allows more of the air/fuel charge in. This can also be negative. This is because if the timing belt or chain breaks, both the piston and the valve it strikes can and will be damaged.

In a non-inference engine, the lift on the camshaft is sufficient to open the valve and allow the charge into the chamber, without opening so far that the valve strikes the piston should the camshaft suddenly stop rotating. This is what happens when the timing belt or chain breaks. This is not true with an interference engine where the camshaft has more lift opening the valve further into the engine cylinder. If the timing belt were to break in a running interference engine, the fully open, stationary valve will be struck by the moving piston resulting in internal damage.

7-A cylinder leak test is usually performed after a cylinder pressure test has indicated a problem. The cylinder is placed on top dead center of the desired cylinder and the spark plug is removed on that cylinder only. This is because when air pressure is introduced into the cylinder the piston will travel downward. The resistance from the other spark plugs helps resist this downward movement.

Once the cylinder is at TDC, air pressure is introduced through a cylinder leak down gauge. These tools often have two gauges, one for inlet pressure and the other for leak down percentage. This second gauge indicates how much pressure the cylinder is actually losing. This loss is measured in percentage which is not to exceed 20 percent. Always check with manufacturers specifications.

Listen for air hissing through the throttle body or carburetor. This indicates a problem with the intake valve. Its allowing compression to seep past the valve and its corresponding seat. Listen for air escaping through the tailpipe. This indicates a problem with a worn or burned exhaust valve. Air escaping through the oil fill cap indicates worn piston rings. Bubbles seen in the radiator neck indicates a leaking head gasket.

8-An engine coolant temperature sensor or ECT sensor is a variable resister. This means that the sensors signal changes or varies according to the temperature of the engine's coolant. The sensors vital in maintaining an engines proper operating temperature. It's located in the coolant stream, usually on or around the thermostat housing. Its constantly sensing the temperature of the engines coolant.There was a day when this sensor was switched either on or off. Now it sends a varying or changing voltage signal to the PCM in relation to the engines temperature. They are NTC or negative temperature coefficient thermistors, and this means that as the coolants temperature increases, its resistance decreases. Another way of saying this is more voltage is dropped across this sensor when its cold than when its hot. The PCM uses these voltage signals to make adjustments to both engine (fans, fuel injectors) and transmission (torque converter clutch) actuators. Faulty coolant temperature sensor symptoms include the engine running too rich and the inability or delay of TCC engagement.

9- Cooling fans are driven by the crankshaft or by an electric motor. They provide air flow through the radiator fins, transferring heat from the engines coolant to the outside air. The radiator will not operate effectively without proper air flow. This air flow is vital, especially while idling or travelling slowly. If mounted to the water pump flange, bent or missing blades cause an imbalance. This can result in damage to the water pumps bearings and seals. Check for cracks and excessive wear in belts and fan blades as part of the initial inspection.

Viscous Fans: Viscous fans are driven by the crankshaft. The typical viscous fan clutch contains silicon oil that may leak from the unit. This thick fluid's viscosity is measured in CST or centistokes. Check the unit for fluid leaks through the seams and around the shaft. They also have a thermostatic spring that should be inspected. It can be checked be releasing it from its seat and measuring the distance between the spring and its retainer. Always check for manufacturers specifications or special procedures.

Electric Fans: Electric fan blades are typically made of plastic. They wear and begin to crack so they should be carefully inspected for wear. Theyre operated by the ECT, or engine coolant temperature sensor that senses the temperature of the coolant. A variable voltage signal is sent to the PCM. The PCM operates the fan motor with the engines cooling fan relay.

10- A catalytic converter is made of an aluminum oxide honeycomb coated with materials like platinum and palladium. They react and remove (CO) carbon monoxide and (HC) hydrocarbon. A two-way catalytic converter works by oxidizing CO and HC to (CO2) carbon dioxide and water. A three-way catalytic converter also removes (NOx) oxides of nitrogen from the exhaust.When a vehicle is running rich, the catalytic converter is working harder and running hotter than it was intended. This heat can damage the substrate and cause it to melt and degrade. This results in excessive back pressure. Sometimes the substrate will become loose. If the converter rattles when tapped with a plastic hammer, it must be replaced.A back pressure tester is used to confirm suspicions of a clogged catalytic converter. Remove the upstream oxygen sensor and install the tester. The specifications will require back pressure to be below ~1.0 psi. at idle, and no more than 4.0 or 5.0 psi. at snap throttle. There's a big difference between a late model and an older model vehicle. Check with the vehicle manufacturers specifications to before proceding.

11-Sometimes air pockets form in the cooling system when the coolant has been drained. The will result is engine overheating. This happens even after the coolant has been added and the cooling system appears to be full. Air can enter the cooling system after changing the water pump or lower radiator hose. This will affect the engine's ability to maintain proper operating temperature.Be careful. Air pockets are removed with patience, and depending on the vehicle, a special procedure or tool. Technicians can use a coolant fill funnel or a special tool that forces coolant into the system. Air is more compressible than coolant and sometimes difficult to remove without a special procedure.Some vehicles have more trouble with air pockets than others. This is typically due to the design of the vehicle, and where the radiator is located in relation to the engine. Cooling system passages are designed to prevent any air or steam pockets from developing. Two types of cooling systems found on today's vehicles are the series and parallel system.A series system flows around the cylinders, then to the back of the block before sending the coolant to the cylinder heads. A parallel system sends the coolant flow around all the cylinders. Coolant flows through passages located beside each cylinder and into the cylinder head instead of sending it to the back of the engine block first. Reverse cooling systems send cooled fluid to the cylinder head first.A thermostat is vital in maintaining an engine's proper operating temperature. Some thermostat designs come with a little hole that allows any trapped air or steam to pass, and a small amount of coolant to flow, others do not.

12-There are three types of sealants manufacturers commonly use to assemble their engines. These are RTV or room temperature vulcanizing sealant, anaerobic sealant, and pipe joint compound. Of the three, pliable silicone sealants like RTV are most common when repairing or rebuilding an engine. This is due to engine vibrations and imperfect surfaces on engine parts. RTV sealant is not to be used in areas with high temperatures like exhaust manifolds. Always use the appropriate sealer recommended by the engine manufacturer for the specific application.

RTV or room temperature vulcanizing sealant is used throughout the engine, sealing all kinds of leaks. If you've been a technician for any length of time, you've used RTV. An aerobic sealant dries in the presence of air, and forms a flexible rubber gasket. This sealant, along with the others mentioned, must be applied to a clean surface. Scrape any old gasket off the surface with a gasket remover, and clean the surface thoroughly for a leak proof seal. Always follow manufacturers specifications and procedures when using any sealant around a sensor or actuator. This sealant may be used in place of a conventional gasket only in specific applications. Sometimes Teflon tape is a great option to help seal threaded parts.

These sealants should be kept out of bolt holes; they will fill the threaded hole and affect the bolts clamping force. Like the oil pan in the illustration, spread the sealant around the inside of the bolt holes, facing the fluid and the inside of the engine.

13-This is a problem with older high mileage engines. The clearance between the piston and the cylinder wall increases leaving excessive clearance between the pistons and their bores. The pistons are typically made of aluminum. When theyre cold, they are at their smallest. As the metal heats up, it expands and fits tighter in the cylinder bore. The clearance between the piston and the cylinder walls has decreased along with the noise. The knocking sound is known as "Piston Slap".

Most pistons are oval shaped, with more diameter around the thrust side than around the piston pin side. As the engine warms, the piston expands and fills in the piston pin side, making it round. These are called cam ground pistons. If there's a slapping noise in the engine that goes away as it warms, run a wet compression test to see if the cylinders seal are within specifications. Always check for TSB's and for any manufacturer's special procedures.

14-Detonation is a problem caused by competing flame fronts in an internal combustion engine. Only one of them is created by the spark plug, the other is undesired. The entire fuel charge of the proper octane is supposed to wait until the spark plug fires. When the charge is ignited out of time and elsewhere in the chamber, a separate and undesired flame front is created. These competing flame fronts create a loud knock in the engine when they collide. This is why so many call detonation "ping or knock".

There is a difference. Mostly about when the flame front started and how it propagates through the chamber. Pre-ignition is when a flame is ignited in the combustion chamber before the spark plug fires. Its usually caused by hotspots, and reveals itself as a slight knocking heard during acceleration. Knock occurs when the peak of the ignition process does not or no longer occurs at the optimal moment in the engine's timing.

Most engines have a knock sensor that retards the engines timing to prevent this harmful condition. This condition raises cylinder pressures. The competing fronts collide creating this audible knock that resonates down the piston, through the bearings, and onto the crankshaft. Ouch!

There are several causes for these conditions. Most have to do with temperature and timing. There are also other factors to think about: has the engine been modified or have there been any changes to the ignition timing recently. Has the customer used a different fuel, fuels octane rating has a lot to do with its ability to resist early or pre-ignition. Check for TSB's in case of any inherent issues with the make and model you are diagnosing.

15-A turbo charger is lubricated by the engine's oil. Its vital to change the oil and coolant at recommended intervals. This is because old and contaminated oil will surely damage a turbocharger's bearings. Todays turbochargers spin well in excess of 100,000 RPM. Thats incredible! These speeds combined with the hot exhaust spinning the turbine wheel create great heat. This is why theyre so often cooled by the engine's cooling system.

This heat is why many manufacturer's recommend cooling the turbocharger by idling the engine for a minute or two before shutdown. When the engine is shut down immediately after an average drive, the oil will harden and little pieces will get into the bearings causing turbocharger bearing failure. When the bearings are faulty, a whining sound will result. This will also damage the shaft and housing. As the bearings wear, the blades on the turbine and compressor wheels can get damaged from the excessive end-play.

16-Superchargers contain roller and needle bearings. This is because they rotate in excess of 10,000 rpm. They are belt driven by the engines crankshaft. Turbochargers are driven by the vehicles exhaust. This is why so many consider a turbocharger a free source of boost. This is different from a supercharger that takes a little power from the engine to create additional boost. Its a great deal because they increase horsepower by ~20 %. This means that a supercharger can make a 300 hp engine produce 360 hp.

Most superchargers are roots-type, positive displacement pump. They contain a pair of two or three lobed vanes that turn as the engine turns. As the vehicle is accelerated, they turn in opposite directions of each other. This turning motion pulls air from its inlet and forces it into the engine cylinders. Before entering the intake, this pressurized air is cooled by an intercooler. Heat is created by air squeezing through the tight gap in the vane lobes. This cooled charge increases the vehicles performance and horsepower.On many superchargers, changing the size of the pulley changes the speed at which the blades turn. The front bearings contain an opening and a removable dipstick or plug to check and service the special high speed lubricant. Depriving a bearing of its necessary lubricant will result in damage and a noisy squeal.Some of today's OEM superchargers are driven by a computer controlled electric motor. These superchargers are very precise; engine computers operate valves and adjust boost. It may turn the boost on and off as required. These superchargers are far more efficient than standard superchargers that operate under all conditions.

Turbo LagTurbo lag is the delay that occurs when accelerating from a stop in a turbocharged engine. The turbine and compressor wheels are not spinning fast enough to create the necessary boost. It takes a certain amount of time to get a turbocharger up to speed. This lag does not occur with a supercharged vehicle. This is because a supercharged engine is driven by the crankshaft and a turbocharged engine is driven by exhaust pressure. Superchargers offer more additional boost when accelerating from a stop.

17-The battery is the first place to look when a vehicle has a slow start or no start condition. Check the battery posts and terminals. Make sure theyre free of corrosion, and that the terminals are firmly fastened to the posts.

Battery: Perform a voltage test using a voltage meter. A good battery will have 12.6 volts. This is because there are 6 cells in series at 2.1 volts each. A specific gravity test is performed with a hydrometer. A fully charged battery will have a specific gravity of 1.265 at 80 F. Perform a battery load test to see if service or replacement is necessary. First determine the load by retrieving the CCA from the battery case and reducing this number by half. The test discharge rate is one half of the batteries cold cranking rating. Apply this load to the battery for 15 seconds. Battery voltage must remain above 9.6 volts at 70 F.

Battery Cables: Perform voltage drop tests on the starter and ground cables. A loose or corroded ground connection between the engine block and battery negative cable will cause a sluggish or no start condition. Battery cables come in different gauges. Years ago battery cables were 6 gauge, because there werent so many accessories requiring higher amperage. Today's vehicles often come with factory 2 and 4 gauge battery cables, capable of handling higher rates of current. A 2 gauge cable is thicker and can handle more current than a 6 gauge cable.

Solenoid and Starter Motor: A starter solenoid is an electromagnetic device that serves two purposes: it completes the circuit between the battery and the starter motor, and moves the starters gear into mesh with the engines ring gear. The starter motor will wear, causing high current draw. Typically the starter motor is removed and replaced, but internal components like brushes, windings, and bushings may be replaced and the starter placed back into service.

Starting System Switches

The neutral safety switch and clutch safety switch are used to prevent startup during undesired situations. Neutral safety switches are found on automatic transmissions. They prevent starter engagement in all gears except park and neutral. Clutch safety switches are found on manual transmissions. They require that the clutch pedal be depressed before starting the vehicle. Both of these switches can be tested with an ohmmeter. If may be necessary to inspect and test the ignition switch. At the heart of the electrical system, it provides power to the starting circuit when placed in the START position.Engine mounts prevent engine vibrations from transferring to the passenger compartment. This is one of the most common causes for engine vibration; this is especially true in front wheel drive vehicles. Many of today's engines have a balance shaft to keep engine vibrations to a minimum. They work like a counter weight to the engines crankshaft. When an engine is out of balance, it will vibrate whenever the engine is running.

Engine mounts are made of rubbers capable of withstanding engine heat, while insulating engine vibrations from the vehicles frame. They break on older vehicles from years of heat and stress. It's a good idea to check the mounts after removing an engine. When they are old, they often break or become damaged during removal/installation.

19-Measure cylinder bore clearance before installing the pistons back into the engine block. Today's vehicles have extremely tight maximum allowable clearances. The cylinders taper and out of round dictate whether a cylinder is acceptable or if the engine block needs to be bored.

Out of Round: An out of round cylinder is out of round when beyond specifications. When a cylinder wall is new it is perfectly round. They must be in excellent condition before piston installation. Pressures exerted at the top of the ring travel and at the thrust and non-thrust surfaces take their toll over time. Pressure is most at the top and at a point 90 to the piston pin. Measure for out of round and taper before reconditioning the cylinder walls.

Taper: Taper is the difference in the diameter of the cylinder between its top and bottom. Take measurements at the top, and compare them to the measurements at the bottom. Taper causes the rings to travel in and out of their grooves as the piston travels up and down the cylinder.

20-Connecting rods and their matching caps are fastened to the engines crankshaft to convert linear motion into rotary motion. They are often constructed together as one piece. Then a process of breaking the cap away from the rod is done at the factory. These rods and caps must remain a matched set. Since the caps are matched with their corresponding connecting rods, it's important to keep the caps in order during disassembly. That's why, if no number is stamped, a mark with the cylinders corresponding number is made by the technician.

Marking the caps with their corresponding rods is done only when necessary. Making an indentation on a connecting rods shaft is a really bad idea. These rods are made of strong metals and often hardened to retain their strength as the engine wears. Even scratching into one of these rods will weaken it, and could end in catastrophe. Most of us have seen a thrown rod protruding out of someone's engine block. So only mark them if you have to, the base is a good spot. Screw the nuts onto the bolts to keep the two parts together

The Process of Elimination

Use the process of elimination. It works great on multiple choice exams like this. Look at the answers and decide which ones do not fit. Eliminate each answer that seems incorrect. Keep going through this process until only one or two answers remain. If only one answer fits, great! As choices are being eliminated, the chance of getting it right increases. Use this method to improve the probability of answering questions on multiple choice exams correctly.

LEAST LIKELY

Take enough time to read the question carefully before you begin the process of elimination. ASE style questions sometimes contain multiple choice questions that contain the term LEAST LIKELY. This changes the normal flow, because with this question the correct answer is something that doesn't fit. Keep this in mind and eliminate answers that are most likely to fit the question.

All EXCEPT ...

ASE will use the word EXCEPT in a question. The correct answer is the answer that doesn't fit. Remember as you're eliminating answers, to eliminate answers that are correct and fit the question. You are searching for the answer that is false. This type of question should be read carefully. Thought must be taken when answering an EXCEPT or LEAST likely type question.