suspension system service

© 2012 Delmar, Cengage Learning

Suspension System Service

Chapter 64


Objectives• Diagnose suspension system problems• Service suspension system components• Describe suspension system repairs• Replace Macpherson struts• Replace suspension bushings


Introduction• This chapter emphasizes the diagnosis and

service of suspension system parts– Commonly performed chassis diagnosis and

repair procedures

• Suspension parts in good condition and properly aligned are subjected to two forces– Car weight on springs and road force of on tires

• Suspension parts take a large amount of abuse– Forces transmitted through the suspension parts

cause wear over time


Diagnosing Suspension System Problems

• Considerations– Carefully question a customer about symptoms

– Entire system IS affected when one part becomes worn

– Spring sag is normal and occurs with the passage of time

– Check all ball joints and bushings for looseness


Shock Absorber Service• Shock absorbers can be functioning poorly

before obvious signs of failure– Defective shock absorber can cause tire “hop”

– Shock can be defective because it is leaking or physically damaged

– Some OE shock absorbers will still work well after 50,000 miles


Testing a Shock• Perform a visual inspection of the shock

– Inspect shock mounts and rubber cushions

– Check for fluid leaks

– Outside of shock is damaged: replace both shocks

– Rubber bump stops show signs of contact: shock could be damaged

– Check shock mounts

– Air shock: sometimes fail when it gets a hole in its rubber bladder

– Gas shock has lost its gas charge: no longer will expand


Macpherson Strut Service• Macpherson strut shock fails

– Common repair procedures• Replace entire assembly• Install a strut cartridge

• Some struts are easily removed at the bottom by removing two bolts– Spring compressor is used to compress the coil

spring

– Some struts can be serviced with a shock cartridge


Inspect the Upper Strut Bearing

and Install the Coil Spring• Inspect the upper strut bearing – Inspect condition of upper strut bearing while

strut is disassembled

• Install the coil spring– Install coil spring and tighten locknut

– Be sure both ends of spring are correctly seated before removing compressor


Reinstall the Strut Assembly• Reinstall in same position as before

– Wheel alignment may be needed after strut replacement

– Brakes will need to be bled if brake caliper was disconnected


Suspension Bushing Service• Bushing characteristics

– Made of synthetic rubber

– Prone to heat damage

– Should not be lubricated

– Deteriorate with age

– Removed by pressing or driving them out


Strut Rod Bushing Service and Stabilizer Bar Service

• Strut rod bushing service– Remove the fasteners

– Most bushings have a center spacer

• Stabilizer bar service– Inspect bushings at both ends of stabilizer bar

– Replace any bushings that are cracked, worn, or weathered


Spindle Service• Replace a steering knuckle or spindle that is

damaged– If a wheel bearing fails it can wear or heat the

spindle• Changes the metallurgy of the spindle and it must

be replaced

• Damage from a collision will be noticed during SAI alignment angle check


Ball Joint Service• Important points and considerations

– Ball joints are relatively trouble-free

– Feel around outside of boot and look for tears

– Always check specifications

– Load-carrying ball joint usually has some movement when unloaded

– Determine whether ball joint is a load carrier or follower


Measuring Ball Joint Wear• Important points and considerations

– Check manufacturer's recommended procedures before checking ball joints

– For an accurate check: ball joint must not support weight of vehicle

– Follower joint should be checked at same time loaded ball joint is unloaded for testing

• To check follower ball joint for movement: unload joint and try to move tire back and forth

– Some ball joints have wear indicators


Separating Tapered Connections

• Loosening the tapered connection on a ball joint can be accomplished using a large hammer– Remove cotton pin from ball joint nut and loosen

nut

– Position vehicle so coil spring is pushing control arm away from ball joint

– Use hammer to pound sharply on steering knuckle on outside of taper


Replacing a Ball Joint• Characteristics

– Some original equipment ball joints are fastened to control arm with rivets

– Ball joints can also be pressed or threaded into hole in control arm

– Some pressed-fit ball joints have a spot weld that hold them in place


Coil Spring Service• Characteristics

– Coil spring will rarely break unless it has been constantly overloaded or has a stress raiser

– Incorrect ride height affects wheel alignment angles, camber, toe, SAI, and scrub radius

– A vehicle that is too low cannot be aligned properly


Adjusting Spring Height and Coil Spring Replacement

• Adjusting spring height– Correct ride height must be restored prior to

alignment

– Coil springs must be replaced when they have sagged beyond specifications

• Coil spring replacement– Replaced in front or rear pairs

– Replacement springs must be of the same kind


SLA Coil Spring Replacement• Major considerations

– During a coil spring replacement: only lower ball joint needs to be removed

– Spring seats must be accurately aligned

– Torsion bar adjusting bolt must be loosened before removing torsion bar

– Leaf spring problems include broken leaves, spring sag, and differences in ride height


Wheel Alignment• Required after suspension repairs

– Repositions suspension components• Car will be safe to drive and will go straight without

unusual tire wear

• Remember to torque bolts that go through bushings only after vehicle is resting on its tires


Electronic Suspension Service• Electronic suspension system problems

– Often related to mechanical failures– Electrical failures can also occur in the air system

• Wiring connections – Common source of problems

• Electronic failures – Set a diagnostic trouble code and cause

instrument panel light to flash

• Electronic suspension systems– Several sensors


Electronically Controlled Shock Absorbers

• Some shock absorbers are electronically controlled– Remove actuator: squeeze plastic retainers to lift

motor from top of strut

• Diagnosing actuator system– Wiring color codes and specific instructions

required

suspension system service

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