Post on 11-Jan-2016
McPherson Strut Service and Diagnosis
Consumer Auto Suspension Lecture 2
How McPherson Struts Work
• Struts combine coil spring, shock, and upper control arm
• Upper bearing provides a place for the strut to swivel
• Helps keep wheel in contact with the road
• How the strut is attached to the car is critical for wheel alignment
Lower Control Arms Function
• Connect frame to steering knuckle
• Has bushings on one end, a ball joint on the other
• Uses a rubber bumper to prevent metal to metal contact
Steering Knuckle Function
• Connects lower control arm to strut
• Swivels on ball joint and upper bearing
Stabilizer Bar Function
• Connects left and right lower control arm
• Connected to vehicle body
• Reduces body roll
Strut Rod Function
• Connects lower control arm and frame
• Holds control arm in position, keeps wheels in alignment
Diagnosing Noise Problems
• Loose mountings• Loose or damaged
struts• Worn or damaged
ball joints• Worn control arm
or stabilizer bushings
Diagnosing Ride Height Problems
• Damaged or broken parts
• Broken or fatigued springs
• Misaligned body mountings
Diagnosing Body Roll Problems
• Bad struts
• Worn stabilizers
• Worn control arm bushings
• Worn ball joints
Control Arms Inspection
• Raise vehicle, inspect for signs of damage
• Pull and push wheel to check for ball joint wear
• Use pry bar to inspect for arm bushing movement
MacPherson Strut Inspection
• Check for oil leaks, bent piston rod or other parts
• Check springs for damage or breaks
• Turn wheel from stop to stop and listen for noise
• Check shock for proper operation
Steering Knuckle Inspection
• Check for damage
Stabilizer Bar and Links Inspection
• Check for damage and broken/missing bushings
• Check for bent parts
• Check for loose bolts
Strut Rod Inspection
• Check for bending
• Check frame bushings
• Check for loose bolts or nuts
Check Connections to Other Parts
• Tighten bolts and nuts
Lubrication
• Use recommended grease
• Follow lube schedule in the owners manual
Suspension Parts are Not Repairable
• Repaired suspension parts are NOT SAFE!!!
• Repaired suspension parts wear out much quicker
Front End Alignment
• Needed after the control arm, steering knuckle or strut has been changed
• Not necessary after stabilizer (sway bar) replacement
Stabilizer Bar Replacement
• Unbolt sway bar brackets
• Unbolt link assemblies and replace
Strut Rod Replacement
• Raise and support vehicle
• Unbolt from the frame
• Unbolt from the control arms
• Remove bolt from lower control arm
• Install new strut rod, bolt to frame, and control arms
• Reinstall bolt in lower control arm
• Torque to specifications
MacPherson Strut Replacement
• Raise and support vehicle
• Mark adjustment cam on lower attachment point
• Unbolt lower and upper attachment
• DO NOT remove shock nut in center
• Remove strut and replace
• Replace all one-time fasteners
Lower Control Arm Replacement
• Raise and support vehicle
• Remove wheel and support
• Disconnect strut rod and stabilizer bar
• Separate ball joint, unbolt from frame
• Replace ball joint, bushings
• Install new part
That Concludes Suspension Lecture 2