1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Chapter 68
Suspension System
Diagnosis and Repair

3. Contents Suspension system diagnosis Shock absorber service
Suspension spring service
Ball joint service
Suspension bushing service
MacPherson strut service
When alignment is needed
Computerized suspension diagnosis

4. Suspension System Diagnosis Symptoms of suspension system problems:
abnormal noises
tire wear
steering wheel pull
front end shimmy

5. Diagnosing the Suspension System
Gather information from the customer or service writer
Inspect the parts that could cause the problems indicated
If necessary, road test the vehicle to verify the complaint

6. Suspension System Problems

7. Front Suspension System

8. Shock Absorber Service
Worn shock absorbers will cause a vehicle to ride poorly
When the tire strikes a bump, a bad shock will not dampen spring oscillations
Loose or damaged shock absorbers may produce a loud clanking noise

9. Checking Shock Absorber Condition
Perform a visual inspection for damage, rubber bushing wear, or oil leakage
Perform a shock absorber bounce test
push down on one corner of the vehicle
release the body
count the number of times the body rebounds
one or two rebounds is acceptable

10. Replacing the Shocks Raise the vehicle on a lift Remove the wheels
Support the control arms or axle housing with a jack or jack stand
Remove the old shock absorbers
Install the new shocks
Install the wheels and torque to specs

11. Replacing the Shocks
Support the control arm to prevent the spring from forcing parts down violently

12. Unbolting the top and bottom of the shock
Replacing the Shocks
Unbolting the top and bottom of the shock

13. Air- and Gas-Charged Shock Service
Gas-filled shocks require replacement when faulty
Air shocks may be repairable
Air leakage may occur at air lines, an air valve, or the shocks themselves
To test, wipe on a soap-and-water solution, watching for bubbles that indicate leakage

14. Suspension Spring Service
Spring fatigue allows a vehicle’s body to settle, lowering the curb height
changes the control arm position
misalignment results
Fatigue can occur after prolonged service

15. Measuring Curb Height Place the vehicle on a level surface
Measure from a specified point on the frame, body, or suspension down to the floor
Compare the distance to specifications
If the curb height is too low, spring replacement or torsion bar adjustment will be necessary

16. Curb Weight
Weight of the vehicle with a full tank of fuel and no passengers or luggage
Vehicle should be at curb weight when measuring curb height
remove everything from the trunk except the spare tire and jack

17. Coil Spring Compressor
Squeezes the coils closer together
Reduces the length of the spring

18. Coil Spring Compressor
Coil spring compressor kit

19. Coil Spring Removal Raise the vehicle on a lift
Support the control arm or axle housing
Remove the shock absorber
Install the spring compressor and compress the spring

20. Coil Spring Removal
If necessary, separate the lower or upper ball joint using a separator tool

21. Coil Spring Removal
Remove any components that could be damaged when the control arm is lowered:
brake line, strut rod, steering linkage
Pull the spring and the compressor out as a unit

22. Coil Spring Installation
Compress the new spring
Slip the spring into place and position the coil ends in the same location as the old spring
Reassemble the ball joint and other components
Unscrew the spring compressor while guiding the coil into place
Install the wheels and lower the vehicle

23. Rear Coil Springs
Lower the axle after unbolting the shocks—the coils will simply fall out

24. Leaf Spring Service
Service usually involves spring or bushing replacement
Place jack stands under the frame
Use a floor jack to raise the weight of the rear axle off the leaf spring
Remove the U-bolts that clamp around the middle of the spring and the axle

25. Leaf Spring Service Slide the through-bolts out of the spring
Remove the old leaf spring
Install the new leaf spring
Reassemble and lower the vehicle

26. Spring Bushing Replacement
Replacing a worn bushing with a driving tool

27. Torsion Bar Service Most torsion bars are adjustable
Replacement is not generally needed unless a torsion bar breaks
When the curb height is too low, tension must be increased to raise the vehicle

28. Torsion Bar Suspension

29. Ball Joint Service
Worn ball joints cause the steering knuckle and wheel assembly to be loose on the control arms
Clunking or popping sounds might be heard when turning or driving over bumps

30. Ball Joint Lubrication
Wear is usually a result of improper lubrication or prolonged use
If dry, the joints can wear out quickly
Grease fittings or lube plugs may be provided
lubricate the joints with a grease gun at regular intervals
Many late-model ball joints are sealed units that do not require lubrication

31. Ball Joint Lubrication
Replace lube plugs with grease fittings

32. Ball Joint Lubrication
Grease the ball joints and other fittings regularly
Only install enough grease to fill the boot

33. Checking Ball Joint Wear
Two methods of checking ball joint condition are commonly used:
ball joint wear indicator
measuring the play in the ball joint

34. Ball Joint Wear Indicator
Part of the ball joint
Inspect when the weight of the vehicle is on the wheels
A shoulder around the grease fitting will recede into the joint as it wears
When the shoulder recedes below the surface, replace the joint

35. Ball Joint Wear Indicator

36. Measuring Ball Joint Play
Jack up the vehicle
weight must be removed from the joint
Physically move the control arm and tire assembly
Use a pry bar while watching for joint movement
Compare the movement to specifications

37. Measuring Ball Joint Play
Lift points for different suspension systems

38. Measuring Ball Joint Play

39. Ball Joint Removal Raise the vehicle on a lift Support the control arm
Remove the shock absorber
Install a coil spring compressor on the spring, if necessary
Remove the nut securing the ball joint to the steering knuckle
Separate the knuckle from the joint

40. Ball Joint Replacement (Press-fit)
Remove and install the ball joint using a ball joint driver

41. Ball Joint Replacement (Riveted)
Drill out the rivet heads
Drive out the old rivets
Bolt on the new ball joint

42. Ball Joint Replacement
If the ball joint is screwed into place, use a large wrench to unscrew the old ball joint
Clean the threads in the control arm
Torque the new joint to specifications
Reassemble the vehicle
Remove the spring compressor, if used
Lower the vehicle

43. Suspension Bushing Service
Rubber bushings are commonly used on the inner ends of the control arms
Bushings should be checked periodically for wear
Worn bushings can let the control arms move sideways, causing tire wear and steering problems

44. Checking Bushing Wear
Try to move the control arm against normal movement
Watch the bushings
If the arm moves in relation to its shaft, the bushings are worn and must be replaced

45. Bushing Removal Procedures vary, refer to a service manual
The stabilizer bar and strut rod must be unbolted from the control arm
Remove the bolts passing through the bushings
Remove the control arm
Bushings are pressed or screwed into the control arm

46. Bushing Removal

47. Using a driver on a pressed-in bushing
Bushing Replacement
Using a driver on a pressed-in bushing

48. Bushing Replacement
With this design, nuts are used to force new bushings into the control arm

49. Bushing Replacement Reinstall the control arm
Torque all bolts properly
Install the ball joint cotter pin and other components
The bushings may require preload with the weight of the vehicle on the wheels
lower the vehicle before tightening the control arm shaft nuts

50. MacPherson Strut Service
The most common problem is worn strut shock absorbers
the seals inside the strut can begin to leak
dampening is reduced
vehicle ride is affected

51. Strut Removal

52. Strut Removal Remove the strut as a single unit
Note the alignment for reassembly

53. Strut Disassembly Use a spring compressor to remove the coil spring
After the spring is squeezed together, remove the upper mount assembly
Release spring tension and lift the spring off the strut
Inspect the parts for wear and bearing roughness
Replace parts as necessary

54. Spring Compressors
Portable
Bench-mounted

55. Strut Assembly Inspection

56. Replacing a Strut Cartridge

57. Assembling the Strut Fit the strut into the compressor
Compress the spring
Install the upper spring seat and mount assembly
Release the spring compressor

58. Strut Assembly

59. Strut Installation
Lift the strut into position in the upper body mount
Attach the lower end of the strut to the steering knuckle or bearing support
Align any reference marks
Install the fasteners
Install any other parts

60. Always torque fasteners to specs
Strut Installation
Always torque fasteners to specs

61. When Alignment Is Needed
After servicing ball joints, control arm bushings, strut rods, springs, strut assemblies, or other suspension parts, wheel alignment must be checked and adjusted
Rapid tire wear or handling problems could occur if the alignment was altered

62. Computerized
Suspension
Diagnosis

63. Computerized Suspension System

64. System Diagnosis Connect a scan tool to the diagnostic connector
Read any stored diagnostic trouble codes
Check the scan data for abnormal suspension-related operating values
If any problems are noted, use pinpoint checks to isolate the source of the problem

65. Scan Tool Display A. Select the desired control module
B. Choose a mode, such as read codes
C. Trouble code display

66. Checking the output signal from a height sensor
Pinpoint Tests
Checking the output signal from a height sensor

67. Pinpoint Tests Voltage waveform from a height sensor
The voltage should rise and fall smoothly as the arm is moved

68. Height Sensor Service
The sensor can fail mechanically due to worn parts, a bent arm, or broken parts
The sensor may also fail electrically, ceasing to produce a normal signal
Replacement is usually required

69. Height Sensor Replacement

70. Compressor Service
A faulty compressor will not produce the air pressure needed to maintain the correct ride height
Check the electrical connections and source of voltage
Connect a pressure gauge to the output hose fitting to measure pressure output
If the pressure is not within specs, replace the compressor

71. Compressor Replacement

72. Electronically-Controlled Shock Service
When replacing the shocks, you may be able to transfer some of the electronic parts from the old units onto the new ones
Do not install conventional shocks to save the customer money
constant trouble codes might be set, and vehicle safety could be adversely affected