Suspension System Service

1. Suspension System Service Chapter 64

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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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