Suspension System Service: Chapter Objectives

C H A P T E R
© Cengage Learning 2014
7
Suspension System Service
Chapter Objectives
At the conclusion of this chapter you should be able to:
t Identify the tools and their correct usage for servicing the suspension system.
t Identify suspension systems and suspension components.
t Perform suspension system component inspections.
t Diagnose suspension system concerns.
t Service components of the suspension system.
t Perform a prealignment inspection.
KEY TERMS
axle puller grease fittings spring compressors
dry-park check prealignment inspection strut spring compressor
electronic stethoscope ride height visual inspection
Copyright 201 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
202 Chapter 7 • Suspension System Service
R epairs on the suspension system are some of the

most common types of repairs technicians per-
form. Because of the operating conditions and the abuse
of everyday driving, suspension components such as
springs and shocks, ball joints, and sway bar links often
require frequent service.
Many technicians begin their careers servicing sus-
pension systems before advancing into other aspects of
vehicle service and repair. This is because suspension
repairs utilize basic hands-on skills and help develop the
critical thinking necessary for all technicians.
Tools and Safety

Every service and repair made to a vehicle must begin
and end with safety in mind. A technician who does not

perform his or her work safely is not an asset; he or she
is a danger. Safe working practices include proper tool
use and care, following the proper repair procedures,
staying focused on the tasks at hand, and taking the time
to perform your work properly.
Figure 7-1 This type of spring compressor is placed inside
Several special tools are used to service the suspen-
the spring and compresses it between the hooks at the top and
sion system, and using them properly will allow you to the fork at the bottom.
work safely and efficiently.
Tools
Without the correct tools, many of the common repairs
made to the automobile would not be possible. When
you are servicing the suspension system, common hand
tools as well as some specialty tools, described below,
are used.
Tools for Suspension Service. Figure 7-1 through

Figure 7-7 show and explain the uses of many of the
tools you will use when you are working on the suspen-
sion system.
Working with coil springs often requires using a
spring compressor. Figure 7-1 shows a spring compres-
sor that attaches to the spring from the inside. This type
of compressor is commonly used with front coil springs.
Figure 7-2 is of a coil spring compressor that attaches
to the outside of the coils. This type of compressor can
be used on struts and other coil springs.
When you are replacing MacPherson strut shock
absorbers, often a spring compressor similar to that
shown in Figure 7-3 is used. The strut is removed from
the vehicle and mounted in the compressor, where it can
safely be disassembled for service.

Installing press fit ball joints and certain types of
suspension bushings requires a special press, shown in
Figure 7-4. The press is needed to install new pressed-in
ball joints without damaging the joint or the control arm. Figure 7-2 This is a type of external spring compressor.
Adapters for the press may be used to remove and install The two clamps attach opposite each other on the spring and
control arm bushings. are tightened evenly to compress the spring.
Chapter 7t Suspension System Service 203
Control arm
bushing

Removal/installer
service tool
FIGURE 7-5 A special tool is used to remove and install some

types of control arm bushings. Some bushings can be driven out
with a hammer and the new bushings pressed back in.

FIGURE 7-3 A strut compressor holds a strut assembly and
allows the spring to be compressed and the strut disassembled
for replacement.
FIGURE 7-6 This tool is used to separate ball joint studs from
components without damaging the studs or grease boots.
SAFETY
Working on the suspension system often requires lifting
heavy objects, working with springs that are compressed,
using air-powered tools, and working with rusted com-
ponents. All of these conditions require extra attention to
safety to prevent injury and damage to the vehicle.
Wheel and tire assemblies can range from around 30

pounds to over 50 pounds. Always use your leg muscles
when lifting, as shown in Figure 7-7. Ask for help when
Position body
FIGURE 7-4 Ball joint presses are used to install press-fit ball
over load
joints and may have adapters to press in control arm bushings.
Weight Keep back

Some control arm bushings will require a specific tool
close to
for service, shown in Figure 7-5. This tool is used to as straight
body as possible
remove and reinstall the bushings without damaging the

bushing or the control arm.
Separating tie rods, ball joints, and other components Use leg
is often easier using a separator tool like the one shown muscles Legs bent
in Figure 7-6. This tool is used so that the studs, threads,
and grease boots of ball joints are not damaged when FIGURE 7-7 Proper lifting requires using your leg muscles
removing them without replacing them. and not those in your back.
it is needed to lift a wheel and tire. Back injuries are Inspection and Service
common among service technicians and can cause long-
term pain and disability. Inspection of the suspension system includes looking at
When you are working with suspension springs, the tires and the steering system. This is because prob-
always follow the proper service procedures for safely lems with the suspension system may show up as tire-
compressing and handling the springs. Check spring wear issues and because there is some sharing of parts
compressors for wear, damage, and proper opera- between the steering and suspension systems.
tion before use. Coil springs can, if released suddenly,
Basic Inspection Procedures
bounce around and cause serious injury and damage to
In every aspect of automotive service and repair, you
vehicles.
first should verify the customer’s complaint. Once you
Replacing suspension components often requires
have done that, your next step is determining the cause
fighting with rusted components and fasteners. Try
of a concern. The best way to begin your diagnosis is to
to clean as much rust from the area as possible with a
perform a thorough inspection. Before any repairs are
wire brush before attempting service. This is especially
made to the suspension system, a complete inspection
important when you are using air tools, such as air
of the system must be performed. One of the best ways
impacts, because rust tends to break off and fly through
to locate possible concerns is by performing a visual
the air. Apply a penetrant to rusted nuts and bolts before
inspection.
attempting to remove them.
Visual Inspection. A technician who performs a
Safe Work Practices. When you are performing good visual inspection can often discover many items that
work on the suspension system, you will often be work- need attention. Use a logical and systematic approach to
ing with springs and other components that require visual inspections rather than randomly looking at com-
special handling procedures. The following are some ponents that may or may not have anything to do with the
general safe work practices for working on the suspen- situation at hand. Begin your inspection by looking over
sion system. the entire vehicle, and consider the following:
• Make sure that the vehicle is properly raised and 1. Does the vehicle appear to lean like the car in Figure 7-8?
supported before beginning any work.
2. How do the tires look? Look at the tread for signs
• Use the proper tool for the job and ensure that the of abnormal wear. Take a close look at the tire in
tool is undamaged and in proper working condition Figure 7-9. Do you see any wear pattern that may be
before use. caused by the suspension system?
• Use the appropriate spring compressors when 3. Based on your knowledge of tires and the suspension
servicing springs and struts. Suspension springs system, what type of problem or component may
can contain a lot of stored energy that, if released relate to the concern?
accidentally, can cause serious injury to people and
damage to the vehicle. Once you have completed this initial overall inspec-
• Before using a strut spring compressor, make sure tion, raise and support the vehicle, and take a look at
you are fully trained in its use and understand how
to safely operate the equipment.
• Shock absorbers contain oil, and some pressurize
the oil with nitrogen gas. Heat should never be
applied to a shock absorber body since the heat
will cause pressure to build in the shock, which
could cause it to rupture, sending hot oil and metal
flying.
• Gas-charged shocks should be relieved of the gas
pressure before disposal. This often is done by
drilling a small hole in the shock body and allowing

the nitrogen to escape. Refer to the manufacturer’s
service procedures before depressurizing a shock or
throwing it away.
• Do not use steel hammers, punches, or chisels on Figure 7-8 This car has a noticeable lean to the left, caused
other steel components. by a broken coil spring.

FIGURE 7-9 Reading tire wear can provide information
about suspension components, such as shocks, that are worn
and need to be replaced. Many times tires provide information FIGURE 7-11 A failed coil spring in a MacPherson strut.
about the wheel alignment, tire pressure, and rotation main-
tenance of a vehicle. Ride Height. As springs age and weaken, vehicle
ride height decreases. Broken springs, like that shown in
Figure 7-11, will cause a very quick and very noticeable
drop in height, but the owner may not notice the gradual
drop over years of service. Once the vehicle ride height
falls below a certain spot, it may be impossible to bring
the wheel alignment back into specification. Addition-
ally, as the springs weaken and sag, their ability to handle
the vehicle’s weight and the constant jounce and rebound
actions that occur while driving are reduced. A weak
spring will be more likely to allow bottoming out of the
suspension, resulting in a much harsher ride.
Vehicle ride height can be checked in several different
places depending on what the manufacturer specifies. One
common way to check ride height, shown in Figure 7-12,
measures the height from the ground to the bottom edge
FIGURE 7-10 Leaking shocks can no longer effectively

dampen the spring and must be replaced.
the suspension parts. Look for any signs of obvious

damage, such as bent or broken parts, or leaking shocks.
Figure 7-10 shows a severely leaking shock absorber.
If nothing stands out as being wrong, proceed to more FIGURE 7-12 Checking vehicle ride height to determine if
specific inspection items. the springs are good.
of the body. Another common method is to measure from

the top of the wheel opening to the ground. Ride height
measurements should usually be close to equal from front
to rear and side-to-side. Always refer to the manufacturer’s
measurements, procedures, and specifications as some
vehicles specify different ride heights at the front and rear.
As a rule, ride height should not vary more than about
one-half of an inch (13 mm) from side-to-side or from
front to rear. If the ride height is incorrect, carefully

inspect the entire suspension, wheels, and tires before
condemning the springs. Remember that replacement
wheels and tires that have a lower or higher profile than
the original equipment wheels and tires will affect ride
height as will the tire pressure.
Figure 7-13 Sometimes you must move piston boots to
Shock Bounce Test. Worn shock absorbers can check to see if a strut is leaking.
be found by performing a shock bounce test. Bounce a
corner of the vehicle up and down three times and count Check the shock upper and lower mounts and bush-
the number of bounces until the vehicle settles to a stop. ings. While it is not a common problem, the shock
Good shocks will usually dampen out in two to three mounts can break, and the bushings can deteriorate,
bounces. More than three bounces may mean the shocks leaving the shock unsecured and rattling around.
are weak and not controlling the spring very well.
Visually inspect the shocks for signs of oil leaks. Any Reading Tire Wear. A very important skill for any-
more than a very slight oil film around the upper piston one who is doing suspension, steering, and alignment
seal means the shock is leaking excessively and needs repairs is the ability to read tiretread wear. The wear on
to be replaced. You may have to move the dust boot a tire can provide a lot of information about the vehicle’s
covering the strut piston to check for a leak strut, like condition and how well it is maintained. Figure 7-14
that shown in Figure 7-13. shows common tire wear conditions and their causes.
Diagonal
Rapid wear Rapid wear Cracked Wear on Feathered Scalloped
Conditions wipe rear tire
at shoulders at center treads one edge edge wear
FWD vehicles
Effect
Excessive Incorrect Incorrect

Underinflation Overinflation
camber toe wheel
or lack of or lack of
toe
rotation rotation
Lack of rotation
Underinflation of tires or worn
Causes or excessive or out-of-
speed alignment
suspension
Adjust Adjust Perform Rotate tires

Adjust pressure to
Corrections camber toe rear and inspect
specifications when tires
to specs to specs wheel suspension
are cool. Rotate tires.
alignment
Figure 7-14 This chart shows examples of tire wear and the common causes.
Chapter 7 • Suspension System Service 207

Figure 7-15 An electronic stethoscope can be very helpful when trying to
determine the cause of a suspension system noise.
Being able to determine what factors are causing tire determine under what conditions the noise occurs, such
wear will help you to accurately diagnose suspension as over bumps, when turning, or when accelerating or
and steering problems. decelerating. You may need to perform the test drive
It is not unusual for a vehicle to show more than one with the customer so that you know exactly what the
type of tire wear. For example, a FWD car that does not customer’s complaint is. If the customer is not available,
have the tires rotated often enough and is only slightly perform a test drive with another technician so both of
out of alignment can show excessive wear on the front you can listen and discuss what could be the cause.
tires while the rear tires appear like new. This is because Sometimes even more help is needed to pinpoint a
the front tires on FWD vehicles wear faster due to vehi- noise. Use of an electronic stethoscope, especially
cle weight distribution and because of the turning and ones made for noise diagnosis like the tool shown in
driving forces applied to them. Figure 7-15, can be extremely helpful. The tool shown
in Figure 7-15 has small microphones that are placed
Noises. Noises can be a challenge for even the most in different locations on the vehicle to help isolate the
experienced technician, but if you have a thorough under- cause of a noise.
standing of the vehicle, its systems, and its components, Table 7-1 provides a list of common suspension
you will be much more likely to be able to quickly deter- noises and the typical causes.
mine the causes of most noises.
Noises can be caused by worn suspension compo- Test Driving. A test drive is often necessary when
nents, such as loose ball joints and strut bearing plates. a technician is trying to determine the cause of a noise
A test drive is usually needed to pinpoint a noise. Try to or vibration. Even though as a student you are not likely
Knocking noise over bumps Loose ball joint, worn strut, worn strut bearing plate,
worn tie rod, worn shock, broken sway bar link
Clunking or knocking on Worn control arm bushings, worn ball joints, worn
acceleration/deceleration FWD CV joint
Creaking or groaning Worn control arm bushings, worn ball joints or tie rods,
broken spring, worn or damaged upper strut plate
Table 7-1 Common suspension noises
to perform test drives, it is an expected and necessary Many sway bar links are one piece and use a ball-
part of being a professional technician. As a student, you and-socket connection, while other sway bar links
may be able to drive the vehicle around the lab or park- are attached with a link kit, made up of bushings and
ing lot enough to confirm the customer’s complaint. Test washers and secured by tightening the nut and bolt.
drives can be extremely important to diagnosing many If one sway bar link is broken, both sides should be
concerns, especially noises and vehicle handling com- replaced.
plaints. Once the problem is diagnosed and repaired, the
test drive confirms that the repair is complete, and the Service History and TSBs. You should also per-
vehicle is ready to be returned to the customer. form a search of the vehicle’s service history and for
any relevant technical service bulletins (TSBs). If the
Body Lean or Sway. While you are test driving vehicle is regularly serviced by your shop, there should
the vehicle, pay attention to how the car body reacts be a service history available. Look through previous
while cornering. Excessive lean or sway is caused by repair orders to check for prior repairs to the suspen-
broken sway bar links. Figure 7-16 shows an example sion or steering systems. This is called checking the
of a broken sway bar link. If the sway bar links are bro- vehicle’s service history, which is often an important
ken, the body will pitch or roll much more than normal source of information about the vehicle. Also, check the
when turning a corner. service information for any TSBs related to the suspen-
sion or steering systems, especially if you are attempt-
ing to diagnose a noise complaint. Figure 7-17 shows
an example of TSBs related to the suspension system.
The few minutes it takes to check these items could
save you hours of work by identifying a known prob-
lem for you.
Front Suspension Service

Inspecting and repairing suspension concerns is often
some of the first work an entry-level technician will per-
form. This is because much of the common suspension
work, such as replacing shocks and struts, is generally
simple and straightforward work.
Remember, the suspension system does not work
alone. It works with the frame, steering system, wheels,
and tires. Therefore, it can be affected by problems in
these other areas.
Strut Service. The most common suspension type in

use today is the strut suspension, whether a MacPherson

strut, modified strut, or part of a multilink arrangement.
Strut components suffer from the same types of prob-
lems as the components of any other type of suspension,
Figure 7-16 Broken stabilizer bar links are a common leaking shocks and worn springs. Struts also can develop
concern and usually cause noises and increased body roll problems with the upper bearing plates that require ser-
during cornering. vice or replacement. To conduct a thorough inspection of
Figure 7-17 Checking for service bulletins can save you hours of diagnostic time.
the strut to determine exactly what repairs are necessary,

check the following:
• Inspect the shock absorbers for leaks and conduct a
bounce test.
• Measure vehicle ride height to check for spring sag.
• Test-drive the vehicle to listen for noises over bumps
and while turning.
• Inspect the strut assembly to see if it is bent from a
collision or other impact.
Strut service usually requires removing the strut from
the vehicle. Removing a typical MacPherson strut is
shown in Photo Sequence 5.
Once the strut is removed, mount it in a strut spring
compressor. Use a grease pencil or paint pen to index
the mount and coil spring for proper alignment. When it
is properly secured and the spring is compressed, remove
the nut holding the strut piston rod to the upper bear-
ing plate. With the nut removed, slowly remove the strut
from the spring and bearing plate. Remove the upper,

and inspect it for wear and damage. Inspect the bearing
or bushing closely. Worn or damaged strut bearings can
cause noise, hard steering, and poor steering return prob-
lems. Turn the bearing by hand, and note any roughness.
Replace the bearing or mount assembly if there are any Figure 7-18 Following the service procedures is very impor-
signs of excessive wear or damage. tant for safety and to prevent damage to the vehicle. This strut
When you are replacing the strut, in many cases, you spring was released when a student removed the strut’s piston
will need to remove the spring insulator, bumpers, and mount nut while the strut was installed in the car. Luckily there
piston rod cover from the old strut and transfer them were no injuries or damage.
to the new unit. The spring insulator goes between the
bottom of the coil spring and the spring seat attached to
the strut. This insulator helps reduce noise as the spring and weakens, allowing the spring to collapse. The piston
moves on the strut. Inspect the insulator for damage, rod cover protects the piston from damage during opera-
and replace it if necessary. The bumper prevents com- tion. Make sure the new strut matches the old strut and
pletely collapsing the spring, called bottoming out, on reassemble the components.
hard impacts. If the bumper shows signs of damage or Install the new strut into the spring and upper mount,
rot, it should be replaced. Also, inspect the bumper for and guide the piston through the mounting hole. Place
signs that the spring has been collapsing. The spring the washer over the piston, and install a new retaining
itself may show signs of wear as the coils come into con- nut. Most struts require the retaining nut to be torqued
tact with each other. This can happen as the spring ages after the strut is reinstalled on the vehicle and the weight
is back on the suspension. It is usually easier to place the
upper strut mount into position and install the bolts or
nuts to hold the strut assembly when reinstalling. Once
Service Note the strut is held in place, reattach the lower section of
the strut to the steering knuckle. Torque all fasteners to
Do not remove the nut that holds the strut
piston to the upper plate. This nut is keeping specifications.
the strut spring compressed and the unit Some vehicles have a replaceable shock cartridge.
together. Removing this nut before the strut is safely In some vehicles, the strut cartridge can be replaced
compressed is dangerous and allows the spring to while the strut is still installed on the vehicle. To
release, as shown in Figure 7-18. This situation can replace the cartridge, a special tool kit may be needed
damage vehicle components, such as drive axle boots, to keep the components aligned properly during dis-
brake lines, and wheel speed sensor wiring. assembly and reassembly. Always follow the service
information for procedures. In general, remove the
210 Chapter 7t Suspension System Service
PHOTO SEQUENCE 5
REMOVING, REPLACING, AND REINSTALLING A MACPHERSON STRUT

PS5-1 Before removing the strut, mark PS5-2 Raise and secure the vehicle on PS5-3 Remove the wheel and tire to
the position of the strut to the body. a lift. access the strut.
Some struts can only be installed in one
way, but others allow for the mount to
be in different positions. Mark the strut
to realign the mount to the body.

PS5-4 Locate the strut-to-knuckle PS5-5 Remove the strut-to-knuckle PS5-6 Remove the knuckle from the
attachment and determine the tools bolts. strut. Be careful not to overextend the
needed to remove the strut. front axle when pulling the knuckle out.

PS5-7 Following the instructions on the PS5-8 Compress the spring and remove PS5-9 Reinstall the strut onto the vehi-
strut compressor, mount the strut in the the shock piston-to-mount nut. Remove cle. Torque all mounting bolts and nuts
compressor so that it is secured properly. the strut body and compare the new and to specifications and torque the piston-
old parts. Transfer any covers and insula- to-mount nut with the vehicle on the
tors to the new strut and install it into floor and the weight on the suspension.
the spring. Hand-tighten the shock pis-
ton nut and release the spring tension.
1. Mount in vice
20 mm 3. Remove strut rod

and drain oil
2. Locate cut line
4. Flare strut body
5. Install new cartridge
6. Torque new nut
3 grooves on cartridge
must line up with 3 pads
in base of reservoir tube
Figure 7-19 Some struts have replaceable cartridges that can be removed without taking apart the strut. © Cengage Learning 2014
upper retaining nut and then the cartridge as shown In general, to release the gas pressure, a small hole is
in Figure 7-19. Ensure that the correct amount of oil drilled in the lower section of the strut or shock to allow
remains in the strut body when you are replacing the the gas to escape. The location to drill the hole may be
cartridge. The oil is there to remove heat from the marked on the strut body for reference.
shock during operation.
Once the worn components have been replaced,
reassemble the strut. Install the upper retaining nut, but
do not torque it until the strut is reinstalled on the vehicle Service Note
and weight is placed on the strut. Do not attempt to depressurize a gas shock
When you are replacing gas-charged struts or shocks, or strut without reading and understanding
the gas charge needs to be released before throwing the the procedure described in the service
strut or shock away. Refer to the shock manufacturer’s information. Personal injury may result from improper
service information before attempting to release the pres- service.
sure in the shock as the location and size of hole varies.
Depending on the age and condition of the vehicle,

replacing the strut assembly may be more cost-effective Safety Warning
than repairing it. This is an option to give to the cus-
!
tomer. A replacement assembly contains the entire strut Always follow all safety precautions when
unit, which simplifies the removal and installation. using any type of torch. Do not use the torch
without proper instruction and supervision.
Shock Inspection and Replacement. Once a Do not apply heat to any chemical or penetrant, as
shock starts leaking oil or fails to adequately dampen a fire may result. Using a torch to heat rusted shock
the springs, it should be replaced. In most cases, shock hardware can result in the rubber bushings catching
replacement is very straightforward and simple, but on fire. Be careful to only heat the hardware enough
always refer to the service information for procedures to allow it to break loose. Do not apply heat directly
and tightening specs. to the shock body as the increase in temperature will
For front shocks on nonstrut vehicles, locate and remove increase the pressure in the shock. This can cause the
the upper shock mount, then remove the lower shock mount shock to burst, causing severe injury and burns.
and remove the shock. When you are installing the new
shock, be sure to replace the bushings and washers in the
correct order, and do not overtighten the bushings. Rear vehicle’s ride height specs and measuring the ride height is
shock replacement is similar but may require the use of a the best way to check for weak and sagging springs. Also
jack to support the rear axle or control arm. visually inspect the springs and the rebound bumpers, as
Since shocks are exposed to the outside world, you shown in Figure 7-21. A bumper that appears shiny means
should expect the mounting hardware to be rusted and that it has been contacting the frame, which can indicate
possibly frozen into place. Apply a penetrant to the shock a weak spring. A rebound bumper that shows damage,
mounting bolts and nuts to ease removal. If the hardware is such as cracking or chunks missing, should be replaced.
severely rusted, applying heat can often help with removal. Many vehicles have rubber spring insulators mounted
If available, an induction heater, such as the Mini-Ductor, between the spring and the body. These insulators are
shown in Figure 7-20, is an excellent tool to heat rusted used to reduce noise when the spring twists slightly as
and seized fasteners. This tool uses high-frequency mag- the vehicle jounces and rebounds. Check the insulators
netic fields flowing through a flexible conductor to heat to make sure they are intact and positioned correctly
metal objects. After a few seconds, the metal is heated and between the springs and the frame.
can be easily removed without any flames. If, however, Inspect torsion bars and their mounts. The mounts can
this type of tool is not available, you may need to use a deteriorate over time and allow the torsion bar to move.
traditional torch to apply heat to a fastener. This often causes a clunking noise when going over
Install the new shocks and torque all fasteners to bumps. Check both the front and rear mounts for damage.
specs. Lower the vehicle and bounce each corner of the Check the crossmember for damage also. Impact damage
vehicle. Make sure there are no noises from the shocks to the crossmember can affect the rear mount and adjuster.
as the vehicle is bounced.
Steering Knuckles. Steering knuckles are subject to
Spring Inspection. As suspension springs age they damage from collisions. This is common if the vehicle slides
become less capable of supporting the weight of the into a curb or other solid object, as sometimes h appens
vehicle; this will cause the vehicle to sag. L
ocating the in poor weather. Sometimes knuckle damage is obvious,
Figure 7-20 This tool allows for safe heating of rusted nuts and bolts without
causing damage. It uses magnetic induction to excite ferrous metals and create heat.

FIGURE 7-23 An axle puller is often necessary to remove a
FWD hub and steering knuckle.
© Cengage Learning 2014 as older cast iron knuckles. Consequently, when you
are working with aluminum knuckles, use extra caution
when separating the ball joints, so you do not damage
the softer aluminum.
FIGURE 7-21 Check the rebound bumpers. If shiny, the Steering knuckle replacement is usually straightfor-
springs have been bottoming out and are likely weak. XBSE0OB38%WFIJDMF SFNPWFUIFXIFFMBOEUJSF
unbolt and remove the brake caliper and rotor. Remove
the tie rod end, and support the lower control arm with
a jack. Remove the upper and lower ball joint nuts, and
separate the ball joint studs from the steering knuckle.
Once the ball joints are loose, simply remove the knuckle.
When you are reinstalling the knuckle, torque all fasten-
ers to specs, and use new cotter pins.
0O'8%WFIJDMFT TUFFSJOHLOVDLMFSFQMBDFNFOUJT
similar but requires removing the drive axle. Remove the
wheel and tire, unbolt and remove the caliper and rotor.
Remove the axle nut and the outer tie rod. Remove the
lower ball joint connection to the knuckle, and remove the
bolts that hold the strut to the knuckle. An axle puller,
similar to the one shown in Figure 7-23, may be needed
to push the axle out of the bearing in the steering knuckle.
%FQFOEJOHPOUIFUZQFPGXIFFMCFBSJOH ZPVNBZCFBCMF
to unbolt the bearing and install it into the new knuckle.
If the bearing is press fit, you may need to replace the
bearing. Install the new knuckle, and torque all fasteners

UPTQFDT6TFOFXDPUUFSQJOTXIFSFBQQMJDBCMF#FBSJOH
replacement is covered in detail in Chapter 5.
Ball Joint Inspection and Replacement. How

FIGURE 7-22 Many suspension components are made of you check for worn ball joints depends on what type
aluminum to save weight. of suspension you are working on and where the load-
carrying ball joint is located. Remember that the load-
but sometimes a small amount of damage will only be carrying ball joint is located in the control arm on which
found when you are trying to set the front wheel alignment. the spring sits.
Many vehicles now use aluminum steering knuckles, Most MacPherson strut suspensions do not have a
like the one shown in Figure 7-22. Aluminum steering load-carrying ball joint, but that does not mean that those
knuckles cannot take the same amount of impact force joints do not wear or need to be replaced, just that you
cL
Ball joint
clearance

Lift point
Lift point
No movement
Figure 7-24 Check for play in the ball joint by supporting Figure 7-25 Support the lower control arm to check for
the front end under the frame, not the control arm. ball joint wear.
have to check them for wear differently. Figure 7-24 when checked this way, though there are a some applica-
shows how to check the ball joint on a MacPherson strut tions that do allow a slight bit of movement. Check the
suspension. service information for ball joint movement specifica-
Jacking the vehicle in the correct location unloads tions before condemning a slightly loose joint as worn
the ball joint, so it can be checked for wear and move- out and needing replaced.
ment. To check ball joints on SLA, modified strut, and Additionally, even though this has been a typical method
many multilink systems, jack the vehicle, and support the of checking ball joint condition, some m anufacturers
lower control arm, as shown in F igure 7-25. Place a pry specify checking ball joint wear by measuring the rota-
bar under the tire, and pry up against the bottom of the tional torque of the joint using a torque wrench, as shown
tire. Most ball joints should have zero vertical movement in Figure 7-26. Always check the service information for
Measure the roational

torque of the ball joint
stud
Figure 7-26 An excessively worn ball joint will be loose and will have a lower rotational
torque than specified.
WORN NEW
Wear Sintered
surfaces iron bearing

Rubber
When ball joint wear causes 0.050"
1.27 mm pressure
wear indicator shoulder to recede ring
within the socket housing,
replacement is required
Figure 7-27 Wear-indicating ball joints use the grease fitting to show wear.
testing procedures and specifications before condemning Lower

a ball joint. control arm
Some ball joints have built-in wear indicators.
An example of good and worn joints are shown in
Figure 7-27. Examine the ball joint where the grease
fitting threads into the base. If the fitting has receded,
the joint should be replaced. Pressing
Ball joint replacement procedures depend on the type tool
of joint and the type of suspension being serviced. Most
FWD vehicles have ball joints that bolt into the lower
control arm. Bolt in joints are replaced by removing
the ball joint to the steering knuckle fastener and then
unbolting the ball joint. Some vehicles have the ball joint
permanently secured to the lower control arm, and the

entire arm must be replaced when the joint is worn.
Many RWD vehicles, as well as most trucks and
SUVs, have press-fit ball joints. These require a ball joint
press to install the new joint. The worn joints are either
pressed from the control arms or hammered out to save
Figure 7-28 Using a ball joint press to install a press-fit ball
time. An illustration of a ball joint press to install a ball
joint into the control arm.
joint is shown in Figure 7-28. To remove a press-fit joint,
first select the correct size adaptor to allow the joint to
pass out of the arm and into the adaptor. Install the press Once the new ball joints are installed, be sure to install
over the joint, and tighten it until the joint pushes out of the grease fitting and grease the joints. Tighten all fasteners
the arm. To install the new joint, select an adaptor to fit to the correct torque spec, and replace all cotter pins with
the base of the joint and an open adaptor to allow the new pins. If the new cotter pin does not go into the stud
joint to pass through the arm into the adaptor. Position because the holes do not align, tighten the nut until the cot-
the joint and press so the joint is centered in the hole in ter pin fits. Do not loosen the nut to install the cotter pin.
the control arm. Tighten the press until the ball joint is
fully seated. Loosen and remove the press and ensure the Control Arm Inspection and Service. Control
joint is fully seated in the arm. arms usually do not require replacement unless dam-
Some ball joints are riveted into the control arm at aged by a collision, though some must be replaced if the
the factory. These rivets must be removed, and the new ball joint is part of the arm and not separately replace-
ball joint is then bolted back into the control arm. Rivets able. Control arm bushings do wear and often require
are usually drilled out and then driven out with a punch. replacement.
Control
arm
Spacer

Bushing
removal tool
Figure 7-30 Using a bushing to tool to remove a control
Figure 7-29 This control arm bushing has broken free of the arm bushing.
outer steel shell, requiring bushing replacement.
Inspect control arms for damage, such as cracking cracking, and damage. Worn strut rod bushings will
and bending, whenever the suspension is inspected. allow the lower control arm to move forward and back
Cracks and bending can result from severe impacts or during driving. This can cause a knocking sound when
collisions. Control arm bushings deteriorate over time accelerating or braking and can cause the vehicle to pull
and can separate, causing noises and handling com- to one side as wheel position changes. Worn radius arm
plaints. Figure 7-29 shows an example of a worn and bushings will have the same affect, allowing the front
damaged control arm bushing. Bushing replacement wheel to move and to cause noise. Worn or damaged strut
generally requires that the control arms be removed rod and radius arm bushings should be replaced and the
from the vehicle. wheel alignment checked.
Removing lower control arms on SLA and modi-
fied strut suspensions will require removing the coil Stabilizer Bars. Stabilizer bars, also called sway
spring and shock absorber. Once the coil spring and bars or antiroll bars, reduce body sway when cornering.
shock are removed, disconnect the lower ball joint at Broken links and worn bushings are common suspen-
the steering knuckle and the sway bar link. Unbolt the sion problems. Broken sway bar links are usually easy to
control arm from the crossmember and remove the see, as shown earlier in this chapter. Even if they are not
arm. Removing the upper control arm does not require broken, inspect the links. The link shown in Figure 7-31
spring removal, but the lower control arm will need to was assembled incorrectly, which will cause rapid wear
be supported. Disconnect the upper ball joint from the of the bushing and possibly a noise complaint.
steering knuckle, and then unbolt the upper control arm Some sway bar links bolt to the lower control arm or
from the frame. strut and to the sway bar using a ball-and-socket joint,
Control arm bushing replacement often requires spe- shown in Figure 7-32. This type of socket often does not
cial bushing tools, such as those shown in Figure 7-30. disassemble easily as the stud tends to spin in the socket
Follow the instructions supplied with the tool to remove when the nut is removed. Because of this, this type of
and install the bushings. Once the bushings are replaced, sway bar link usually requires replacement if it needs
reinstall the control arm. In many cases the control arm to be removed, even for other types of service, such as
bushings have to be torqued with the control arm in its strut replacement.
normal ride height position. Always follow the manu- Some vehicles have a sway bar link kit that contains
facturer’s service information for proper torquing pro- bushings, washers, a sleeve, and a bolt and nut. This type
cedures and specs. of link must be assembled to connect the control arm
to the sway bar. A common type of this link is shown
Strut Rods and Radius Arms. Vehicles with lower in Figure 7-33. This link also over time tends to rust,
control arms with only one mounting bushing will also making disassembly difficult. It is not uncommon for
have a strut rod. Inspect the strut rod bushings for rot, the link bolt to break during an attempt to loosen and

FIGURE 7-31 Take a close look at this sway bar link. It is
important to pay attention to how pieces fit together.
FIGURE 7-33 An example of a sway bar link kit installed on

a GM car.
To replace sway bar links like those shown in

Figure 7-32, first try to remove the nut securing the
ball studs. In many cases, the stud will spin, making
removal difficult. Some of the studs have an internal
hex built into the end of the stud. This allows you to
install a hex driver or Allen wrench to hold the stud
from turning while loosening the nut. If this does not
work, you may have to cut the nut or stud. Once the old
link is removed, install the new link and tighten the nuts
to specifications.
To replace sway bar links shown in Figure 7-33,
remove the nut, washers, bushings, sleeve and bolt. If it
is seized, you may have to cut the link in half to remove
it. When installing the new parts, make sure you place
the washers and bushings in the correct order. Wash-
ers are placed against bushings to isolate metal compo-
nents and prevent noise. Once assembled, tighten them
FIGURE 7-32 This type of sway bar link uses ball-and-socket to specifications or until the bushings compress to the
joints, which often do not come apart easily and usually require EJBNFUFSPGUIFXBTIFST%POPUPWFSUJHIUFO
replacement once removed. Inspect the sway bar bushings and mounts. The
bushings isolate the sway bar from the body or frame.
remove the link. Because both types of links often do Replace the sway bar bushings if they are rotted,
not disassemble without damage, it is a good idea to cracked or falling apart. Make sure the bushing mounts
include the cost of replacing these components into an or brackets hold the sway bar securely in place. A loose
estimate for services whenever the sway bar link needs bracket will allow the sway bar to knock against the
to be removed. frame or body.
inject grease. Watch the grease boot as you put grease in.
Many boots will expand and release excess grease when
full, but some will continue to expand until the pres-
sure ruptures the boot. Wipe any excess grease from the
grease fitting and around the boots so that it does not get
onto other parts. Your customer will not be happy if the
excess grease from a tie rod spills over onto the wheel
and makes a greasy mess.
Rear Suspension Service

Most of the repairs to the rear suspension are similar to

those performed on the front suspension.
Rear Strut Service. Rear strut replacement is nearly

identical to that for front struts. Rear struts, unless they
are on a four-wheel steering car, do not have bearings in
Figure 7-34 An example of a grease fitting. the upper strut mount, so strut service is typically just
replacement of the shock portion or replacing the entire
Suspension System Lubrication. Even though unit if both the spring and shock need to be replaced.
most modern vehicles have sealed and lubricated-for-life Many rear struts bolt either into the trunk or into the
suspension and steering joints, there are some that still rear firewall area where the rear seatback and parcel shelf
require periodic lubrication. Grease fittings, or Zerk fit- are located. Check the service information about how
tings, are small, nipple-like fittings threaded into a com- to remove the rear shocks or struts before beginning to
ponent for the injection of grease. A small, spring-loaded work. In some cases, the rear seats and trim must be
check ball inside the fitting allows grease in but keeps it removed to replace the rear struts. If so, you may want
from being pushed back out. Figure 7-34 shows a grease to start the replacement procedures by removing the
fitting on an outer tie rod end. upper strut connections first, before getting dirty work-
For most vehicles, high-pressure chassis grease is ing on the lower strut mount. You do not want to get very
acceptable for joint lubrication, but always refer to the dirty and then find out you must disassemble the rear
manufacturer’s service information to ensure that the passenger compartment to access the upper strut mount.
correct grease is used. Shock Inspection and Replacement. Rear shocks
Figure 7-35 shows how to lubricate front suspension are subject to the same wear and damage as the front
and steering components. When you lubricate suspen- shocks, and should be inspected for oil loss and bounce
sion and steering joints, first wipe the old grease and control just like the front shock absorbers. When you are
dirt from the grease fitting. This prevents the dirt from removing and installing the shocks, using a floor jack
being injected into the joint with the new grease. Then or other adjustable jack to support the rear axle will be
attach the end of the grease gun to the fitting and slowly helpful, since you will be able to raise or lower the axle
as needed to align the shock mounting bolts.
When you are replacing the rear shocks, the rear axle
should be supported. Place a jack or jack stands under the
Lube fitting
rear axle before removing the shock fasteners. Remove
Nozzle the shock mounting bolts, nuts, and hardware. When you
are installing the shocks, if a rubber mounting bushing
is being used to connect the shock to the body or frame,
do not overtighten the bushings. Tighten all fasteners to
specs. If a tightening spec is not available, tighten until
the rubber bushing is squeezed to the same diameter as

the washer is against.
Track Bars and Control Arms. Many rear suspen-

sion systems use track bars or control arms to limit rear
Figure 7-35 Using a grease gun to inject grease into a axle movements. Both track bars and control arms are
steering component. subject to damage from collisions and impacts and can
be bent. This will cause the rear axle to be misaligned v ibration issues. Also check the tire sidewalls and wheels
to the body and will affect wheel alignment. Inspect for for damage. A bent wheel may not have a large impact on
damage and replace as necessary. the overall wheel alignment, but it will probably cause
As with other suspension parts, track bars and control a vibration the customer can feel, which could be inter-
arm are attached with bushings. Bounce the vehicle and preted as you not having correctly performed the wheel
listen for any noise from the bushings. Raise the vehicle alignment.
and inspect the bushings for rot, cracking, and damage. A broken spring will usually be obvious since the
Worn bushings can make noise and allow for changes vehicle will be sitting lower in one corner. However,
in rear axle position, which will affect wheel alignment. spring sag that occurs over time is generally not as
Replace any worn or damage bushings. noticeable. Locate the ride height specs, and measure
the ride height. If the height is incorrect, either too high
Rear Spring Service. Inspect the rear coil springs from vehicle modifications or too low from modifica-
for sagging by checking ride height. Check the spring tions or weak springs, the wheel alignment will prob-
insulators between the spring and body and the spring ably be affected. Check for signs of modifications, such
and axle. Worn insulators can cause noise as the vehi- as lowering springs, lift kits, or similar items. Be sure
cle goes over bumps. Check rear leaf springs for broken that the customer is aware that incorrect ride height may
leaves, broken brackets that hold the springs together, mean that the wheel alignment may not be able to be set
damaged insulators between leaves, and for worn or to specs or even to a decent position.
damaged shackles and bushings. Inspect the area of the A quick way to test the shock absorbers is to give each
frame where the leaf spring shackles are mounted as this corner of the vehicle three bounces and count the num-
is a common rust-through location. ber of rebounds there are until movement stops. Good
On RWD vehicles, check where the leaf springs attach shocks will usually dampen out within one and a half
to the rear axle housing. A centering pin is used to keep to two bounces. If the vehicle bounces more than two
the axle from moving but this pin can rust or break. This to three times, the shock and/or struts may need to be
allows the rear axle to shift, which causes serious thrust replaced.
angle and wheel alignment concerns.
Detailed Inspection. Perform a careful inspection
Wheel Alignment of steering and suspension components. Be sure to check
ball joint wear and play, wheel bearings, control arm
Even though performing wheel alignments is not within
bushings, and all steering linkage ball-and-socket joints.
the scope of this text, you should be able to perform
One method of checking the steering linkage is the
a prealignment inspection. This is done to determine
dry-park check. This involves placing the vehicle on
whether or not the vehicle is able to be aligned. If any
a drive-on-style lift, such as an alignment lift. Have a
of the steering or suspension components that affect
helper sit in the driver’s seat, and raise the vehicle until
wheel alignment are worn or damaged to the point where
you can comfortably stand under the front suspension.
the alignment will be affected or will not be able to be
With the engine off, have your helper rock the steering
set, those components will need to be replaced before
wheel back and forth just off steering wheel center as
attempting to align the wheels.
you watch and listen to the steering linkage. Loose com-
Prealignment Inspection ponents will often be easily visible and may even make
Before a vehicle can have a wheel alignment performed, popping noises. By moving the steering with the engine
it must be inspected. Typically, a two-part inspection will off, the weight of the front of the vehicle puts stress on
take place. The initial check is the visual inspection. If the linkage as the tires are pushed back and forth, allow-
the vehicle passes this, then a more detailed inspection ing you to identify loose components.
is performed. Locate the vehicle ride height specs, like those shown
in Figure 7-36, and measure the ride height as indicated.
Visual Inspection. A good visual inspection should Some vehicles may not have specific measurements but
include looking at the tire wear patterns and making sure will instead state that the ride height should not differ by
the wheels and tires are the correct size and are inflated more than a certain amount, often about one-half inch,
properly. Check the tire placard for size and inflation from either side-to-side or front to rear.
information. A vehicle with different tire tread designs Test driving is the best way to get a feel for how the
can experience ride and handling issues due to the dif- vehicle rides and handles. Perform test drives for align-
ferent ways each tire responds to the road. Both front ments over several types of road conditions to get an
tires should be exactly the same size, type, and have the adequate understanding of how the vehicle performs.
same tread pattern to prevent any tire-induced pulling or You should drive where you can take several corners or
Measure at Point A and

Point B. Reading should
vary no more than .5''
(13 mm) from A to B or
from side-to-side.

A B Vehicle
Turbo X A. 7.4'' B. 7.2''
Sedan A. 8.75'' B. 9.0''
Truck A. 9.8'' B. 10''
Figure 7-36 An example of ride height specifications.
sharp turns and drive on both flat and crowned roads. Pay student or technician to help narrow down the possibili-
attention to how the vehicle responds to steering input, ties. Using a stethoscope or Chassis Ear is another way
listen for any noises, and feel if there is any pulling or to help identify the cause of a noise.
leading to the right or left. Broken sway bar links will allow the vehicle to sway
Noises can be caused by loose steering and suspension or roll excessively when cornering. When test driving,
components, defective shock absorbers, broken sway bar pay attention to how the body responds when making a
links, loose wheel bearings, and even from the springs turn. A broken sway bar link can also cause a knocking
themselves. Determining the exact cause of a noise can sound from the front end as the sway bar moves up and
be a challenge. You may need to enlist the help of another down during turns and contacts the broken link.
SUMMARY
Suspension system repairs are some of the most common As the springs age and weaken, vehicle ride height will
types of repairs technicians perform. decrease.
Safe working practices include proper tool use and care, Worn shock absorbers will generally bounce more than
following the proper repair procedures, staying focused two to three times when performing a shock bounce test.
on the tasks at hand, and taking the time to perform your
A test drive is often necessary when trying to determine
work properly.
the cause of a noise or vibration.
Follow the proper service procedures for safely com-
Special tools may be required to remove and install a
pressing and handling the springs.
torsion bar.
A thorough inspection of the suspension system must be
When working with aluminum knuckles, use extra cau-
performed before beginning any repairs.
tion so you do not damage the softer aluminum.
REVIEW QUESTIONS
1. When servicing MacPherson struts, a 4. Before replacing loose ball joints, you should first
is needed to safely disassembly the check the for the wear
strut assembly. specifications.
2. If the vehicle ride height is lower than 5. A or fitting is used
specification, the are likely weak and to lubricate ball joints and other front end
need to be replaced. components.
3. Oil loss, noise, or
indicate a shock absorber needs to be replaced.
6. Technician A says most front suspension springs 9. Technician A says if a vehicle’s ride height is
are coil springs. Technician B says some vehicles below specifications, a wheel alignment can still be
use torsion bars as the front springs. Who is performed. Technician B says if ride height is too
correct? low, the shocks and springs are weak and need to
a. Technician A c. Both A and B be replaced. Who is correct?
b. Technician B d. Neither A nor B a. Technician A c. Both A and B
b. Technician B d. Neither A nor B
7. A knocking sound from the front suspension is
heard during turns: Technician A says a broken 10. All of the following statements about front
sway bay link may be the cause. Technician B says suspensions are correct except:
a worn sway bar bushing may be the cause. Who is a. Most strut suspensions eliminate the upper
correct? control arm and ball joint.
a. Technician A c. Both A and B b. The load-carrying ball joint is in the control arm
b. Technician B d. Neither A nor B on which the spring sits.
8. A FWD vehicle has been in a collision, and the c. The load-carrying ball joint on a MacPherson
left front wheel is notably leaning in at the top: strut suspension is the lower joint.
Technician A says the steering knuckle may be d. The nonload-carrying ball joint is called a
damaged. Technician B says the lower control arm following ball joint.
is bent. Who is correct?
a. Technician A c. Both A and B
b. Technician B d. Neither A nor B

Suspension System Service: Chapter Objectives

Uploaded by

Copyright:

Available Formats

Suspension System Service: Chapter Objectives

Uploaded by

Document Information

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Suspension System Service: Chapter Objectives

Uploaded by

Copyright:

Available Formats

C H A P T E R

© Cengage Learning 2014

R epairs on the suspension system are some of the

Tools and Safety

© Cengage Learning 2014

Tools for Suspension Service. Figure 7-1 through

safely be disassembled for service.

© Cengage Learning 2014

FIGURE 7-5 A special tool is used to remove and install some

© Cengage Learning 2014

© Cengage Learning 2014

Wheel and tire assemblies can range from around 30

Weight Keep back

remove and reinstall the bushings without damaging the

­drilling a small hole in the shock body and allowing

© Cengage Learning 2014

© Cengage Learning 2014

FIGURE 7-10 Leaking shocks can no longer effectively

dampen the spring and must be replaced.

the suspension parts. Look for any signs of obvious

of the body. Another common method is to measure from

© Cengage Learning 2014

Excessive Incorrect Incorrect

Adjust Adjust Perform Rotate tires

© Cengage Learning 2014

Front Suspension Service

Strut Service. The most common suspension type in

use today is the strut suspension, whether a MacPherson

the strut to determine exactly what repairs are necessary,

© Cengage Learning 2014

© Cengage Learning 2014

© Cengage Learning 2014

© Cengage Learning 2014

© Cengage Learning 2014

© Cengage Learning 2014

20 mm 3. Remove strut rod

2. Locate cut line

4. Flare strut body

5. Install new cartridge

6. Torque new nut

Depending on the age and condition of the vehicle,

© Cengage Learning 2014

bearing. Install the new knuckle, and torque all fasteners

Ball Joint Inspection and Replacement. How

© Cengage Learning 2014

Measure the roational

© Cengage Learning 2014

testing procedures and specifications before condemning Lower

© Cengage Learning 2014

© Cengage Learning 2014

© Cengage Learning 2014

© Cengage Learning 2014

FIGURE 7-33 An example of a sway bar link kit installed on

To replace sway bar links like those shown in

Rear Suspension Service

© Cengage Learning 2014

Rear Strut Service. Rear strut replacement is nearly

the rubber bushing is squeezed to the same diameter as

Track Bars and Control Arms. Many rear suspen-

drilling a small hole in the shock body and allowing