by
Russell Krick
Publisher
The Goodheart-Willcox Co., Inc.
Tinley Park, Illinois
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
 Symptoms of suspension system
problems:
 abnormal noises
 tire wear
 steering wheel pull
 front end shimmy
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
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Permission granted to reproduce for educational use only
Suspension System
Problems
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Front Suspension System
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 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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Checking Shock
Absorber Condition
 Perform a visual inspection for damage,
rubber bushing wear, or oil leakage
 Perform a shock absorber bounce test
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© Goodheart-Willcox Co., Inc.
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
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Replacing the Shocks
Support the control arm to prevent the
spring from forcing parts down violently
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Replacing the Shocks
Unbolting the top and bottom of the shock
© Goodheart-Willcox Co., Inc.
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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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
 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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
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Permission granted to reproduce for educational use only
Coil Spring
Compressor
 Squeezes the coils
closer together
 Reduces the length
of the spring
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Permission granted to reproduce for educational use only
Coil Spring
Compressor
Coil spring compressor kit
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
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Permission granted to reproduce for educational use only
Coil Spring Removal
If necessary, separate the lower or upper
ball joint using a separator tool
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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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Rear Coil Springs
Lower the axle after unbolting the shocks—
the coils will simply fall out
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Spring Bushing
Replacement
Replacing a worn bushing with a driving tool
© Goodheart-Willcox Co., Inc.
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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
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Permission granted to reproduce for educational use only
Torsion Bar Suspension
© Goodheart-Willcox Co., Inc.
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 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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Ball Joint Lubrication
Replace lube plugs with grease fittings
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Ball Joint
Lubrication
Grease the ball joints
and other fittings
regularly
Only install enough
grease to fill the boot
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Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Ball Joint Wear
Indicator
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Measuring Ball Joint
Play
Lift points for different suspension systems
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Measuring Ball Joint
Play
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Ball Joint Replacement
(Press-fit)
Remove and install the ball joint using
a ball joint driver
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Permission granted to reproduce for educational use only
Ball Joint Replacement
(Riveted)
Drill out the
rivet heads
© Goodheart-Willcox Co., Inc.
Drive out the
old rivets
Bolt on the new
ball joint
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
 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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
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
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Permission granted to reproduce for educational use only
Bushing Removal
© Goodheart-Willcox Co., Inc.
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Bushing Replacement
Using a driver on a pressed-in bushing
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Bushing Replacement
With this design, nuts are used to force
new bushings into the control arm
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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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
 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
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Permission granted to reproduce for educational use only
Strut Removal
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Strut Removal
 Remove the strut as a
single unit
 Note the alignment for
reassembly
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Permission granted to reproduce for educational use only
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
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Permission granted to reproduce for educational use only
Spring Compressors
Portable
Bench-mounted
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Strut Assembly
Inspection
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Replacing a Strut
Cartridge
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Assembling the Strut
 Fit the strut into the compressor
 Compress the spring
 Install the upper spring seat and mount
assembly
 Release the spring compressor
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Strut
Assembly
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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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Strut Installation
Always torque
fasteners to specs
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Permission granted to reproduce for educational use only
 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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only
Computerized
Suspension
System
© Goodheart-Willcox Co., Inc.
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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
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Permission granted to reproduce for educational use only
Scan Tool
Display
A. Select the desired
control module
B. Choose a mode, such
as read codes
C. Trouble code display
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Pinpoint Tests
Checking the output signal from
a height sensor
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Pinpoint Tests
 Voltage waveform
from a height sensor
 The voltage should
rise and fall smoothly
as the arm is moved
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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
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Height Sensor
Replacement
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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
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Compressor
Replacement
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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
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only