© Goodheart-Willcox Co., Inc.. Suspension system diagnosis Shock absorber service Suspension spring...


Suspension system diagnosis Shock absorber service Suspension spring service Ball Joint service

(8 Topics)


Suspension bushing service MacPherson strut service Wheel alignment is needed Computerized suspension diagnosis


Symptoms of suspension system problems:◦ abnormal noises◦ tire wear◦ steering wheel pull◦ front end shimmy


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

Diagnosing the Suspension System


Suspension System Problems


Front Suspension System


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 as the loose parts bang against the body


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◦ maximum two or three oscillations

Checking Shock Absorber Condition


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 shock Install the wheels and torque to specs

Replacing the Shocks


Support the control arm to prevent the spring from forcing parts down violently



Unbolting the top and bottom of the shock



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

Air- and Gas-Charged Shock Service


Spring fatigue allows a vehicle’s body to settle, lowering the curb height◦ changes control arm position◦ misalignment results

Fatigue can occur after prolonged service


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

Measuring Curb Height


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

Curb Weight


Squeezes the coils closer together.

Reduces the length of the spring

Coil Spring Compressor


Coil spring compressor kit

Coil Spring Compressor


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

Coil Spring Removal


If necessary, separate the lower or upper ball joint using a separator tool

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

Coil Spring Removal


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

Coil Spring Installation


Lower the axle after unbolting the shocks–the coils will simply fall out

Rear Coil Springs


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

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

Leaf Spring Service


Replacing a worn bushing witha driving tool

Spring Bushing Replacement


Most torsion bars are adjustable Replacement is not generally needed

unless a torsion bar breaks When curb height is too low, tension

must be increased to raise the vehicle

Torsion Bar Service


Torsion Bar Suspension


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


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 joints with a grease gun at regular

intervals Many late model ball joints are sealed

units that do not require lubrication

Ball Joint Lubrication


Replace lube plugs with grease fittings



Grease the ball joints and any other fittings

provided regularly


Only install enough grease to fill the boot


Two methods of checking ball joint condition are commonly used:◦ ball joint wear indicator◦ measure the play in the ball joint

Checking Ball Joint Wear


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

Ball Joint Wear Indicator


Ball Joint Wear Indicator


Jack up the vehicle◦ weight must be removed from the joint

Physically move the control arm and tire assembly

Use a pry bar, watching for joint movement

Compare movement to specifications

Measuring Ball Joint Play


Lift points for different suspension systems



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

Ball Joint Removal


Remove and install ball joint usinga ball joint driver

Ball Joint Replacement(Press-fit)


Drill out the rivet heads

Ball Joint Replacement(Riveted)

Drive out the old rivets

Bolt on the new ball joint


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

Ball Joint Replacement


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


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

Checking Bushing Wear


Procedures vary, refer to a service manual

Stabilizer bar and strut rod must be unbolted from the control arm

Remove bolts passing through the bushings

Remove the control arm Bushings are pressed or screwed into the

control arm

Bushing Removal


Bushing Removal


Using a driver on apressed-in bushing

Bushing Replacement


With this design, nuts are used to force new bushings into the control arm

Bushing Replacement


Reinstall the control arm Torque all bolts properly Install the ball joint cotter pin and other

components Bushings may require preload with the

weight of the vehicle on the wheels◦ lower the vehicle before tightening control arm

shaft nuts

Bushing Replacement


The most common problem is worn strut shock absorbers◦ seals inside the strut can begin to leak◦ damping is reduced◦ vehicle ride is affected


Strut Removal


Remove the strut as a single unit. Note the

alignment for reassembly

Strut Removal


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

Strut Disassembly


Portable

Bench-mounted

Spring Compressors


Strut Assembly Inspection


Replacing a Strut Cartridge


Fit the strut into the compressor Compress the spring Install the upper spring seat and mount

assembly Release the spring compressor

Assembling the Strut


Strut Assembly


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

Strut Installation


Always torque fasteners to specs

Strut Installation


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 alignment is altered


Computerized Suspension System


Connect a scan tool to the diagnostic connector

Read any stored diagnostic trouble codes Check scan data for suspension-related

operating values If any problems are noted, use pinpoint

checks to isolate the source of the problem

System Diagnosis


A. Select the desired control module

B. Choose a mode such as read codes

C. Trouble code display

Scan Tool Display


Scoping the output signal froma height sensor

Pinpoint Tests


Voltage waveform from a height sensor.

Voltage should rise and fall smoothly as

the arm is moved

Pinpoint Tests


Sensor can fail mechanically due to worn parts, a bent arm, or broken parts

Sensor may also fail electrically, ceasing to produce a normal signal

Replacement is usually required

Height Sensor Service


Height Sensor Replacement


A faulty compressor will not produce the air pressure needed to maintain the correct ride height

Check the electrical connections and source voltage

Connect a pressure gauge to the output hose fitting to measure pressure output

If the pressure is not within specs, replace the compressor

Compressor Service


Compressor Replacement


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

Electronically-ControlledShock Service

© Goodheart-Willcox Co., Inc.. Suspension system diagnosis Shock absorber service Suspension spring...

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Transcript of © Goodheart-Willcox Co., Inc.. Suspension system diagnosis Shock absorber service Suspension spring...