© 2012 delmar, cengage learning suspension system service chapter 64
TRANSCRIPT
© 2012 Delmar, Cengage Learning
Suspension System Service
Chapter 64
© 2012 Delmar, Cengage Learning
Objectives• Diagnose suspension system problems• Service suspension system components• Describe suspension system repairs• Replace Macpherson struts• Replace suspension bushings
© 2012 Delmar, Cengage Learning
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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
© 2012 Delmar, Cengage Learning
© 2012 Delmar, Cengage Learning
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
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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
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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
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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
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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
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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