A vehicle's braking system is designed to slow down or stop the vehicle by
converting kinetic energy (motion) into heat energy. Here's a simplified overview:
Hydraulic System (Most Common):
When the brake pedal is pressed, it pushes a piston in the master
cylinder.
This pressurizes the brake fluid in the hydraulic lines.
The pressurized fluid travels to the wheel cylinders or calipers at each
wheel.
Wheel cylinders push brake shoes against the drums (drum brakes), or
calipers squeeze brake pads against the rotors (disc brakes).
Friction between the shoes/pads and drums/rotors slows down the
wheels.
Power Assist (Booster):
Most modern vehicles use a power booster (vacuum or hydraulic) to
amplify the force applied to the brake pedal.
This reduces the effort required by the driver to apply the brakes.
Anti-lock Braking System (ABS):
ABS prevents the wheels from locking up during hard braking.
Sensors monitor wheel speed, and the ABS control unit modulates
brake pressure to prevent wheel lock.
This helps maintain vehicle stability and steering control during
emergency braking.
Electronic Brakeforce Distribution (EBD):
EBD works in conjuction with the ABS system.
It distributes the brake force between the front and rear wheels based
on the vehicles load, and road conditions.
This helps to prevent rear wheel lock up.
Electronic Stability Control (ESC):
ESC uses the braking system to help correct a vehicles path when it
begins to skid.
Sensors determine if the vehicle is going in the direction the driver is
steering, and if not, the system will apply individual brakes to correct
the vehicles path.
Safety Procedures and Preparatory Steps
When working on a braking system, safety is paramount. Here's a breakdown of the
procedures:
Place Fender Covers:
Protect the vehicle's paintwork from scratches and spills by placing
fender covers over the fenders.
Follow Safety Procedures:
Wear appropriate personal protective equipment (PPE), such as safety
glasses and gloves.
Work in a well-ventilated area.
Be aware of the potential hazards of brake fluid (corrosive).
If working on a vehicle with air brakes, make sure the air pressure is
bled off.
Never work under a vehicle supported only by a jack. Use Jack stands.
Select Appropriate Tools and Equipment:
Gather the necessary tools, such as wrenches, sockets, screwdrivers,
brake spring tools, and brake bleeding equipment.
Ensure that all tools are in good condition.
Have the proper replacement parts on hand.
Choke Wheels:
Prevent the vehicle from rolling by placing wheel chocks behind the
wheels that are not being worked on.
Disconnect Battery:
Disconnect the negative terminal of the battery to prevent accidental
electrical shorts, especially when working on vehicles with ABS or
electronic braking systems.
Disconnect Pedal Connections:
If necessary, disconnect the brake light switch or any other electrical
connections to the brake pedal.
If replacing the master cylinder, the push rod will need to be
disconnected.
If working on a vehicle with a mechanical parking brake, that will need
to be disconnected.
Identifying Worn-Out Brake Components
Common Faults:
o Pads (Disc Brakes):
Visual:
Reduced thickness: Brake pads have a minimum
thickness specification. Check for wear indicators or
measure the pad thickness.
Uneven wear: Indicates caliper or rotor problems.
Cracks or damage: Caused by excessive heat or age.
Scoring: Caused by debris trapped between the pad and
rotor.
Aural/Feel:
Squealing or grinding noises: Often caused by worn pads
or wear indicators contacting the rotor.
Vibration or pulsation: Can indicate warped rotors or
uneven pad wear.
o Drum (Drum Brakes):
Visual:
Scoring or grooving: Caused by worn shoes or debris.
Cracks or damage: Due to excessive heat or age.
Out-of-roundness: Can cause pulsation or vibration.
Excessive rust.
Aural/Feel:
Grinding or scraping noises: Indicates worn shoes or
drum damage.
Pulsation or vibration: Can indicate drum damage.
Poor parking brake holding ability.
o Shoes (Drum Brakes):
Visual:
Reduced lining thickness: Brake shoes have a minimum
lining thickness specification.
Uneven wear: Indicates drum or hardware problems.
Cracks or damage: Due to excessive heat or age.
Glazing of the friction material.
Aural/Feel:
Grinding or scraping noises: Indicates worn shoes or
drum damage.
Poor parking brake holding ability.
Adjusting Brakes According to Specification:
Bleeding Brakes:
Bleeding brakes removes air from the hydraulic brake system. Air in
the system can cause a spongy brake pedal and reduced braking
performance.
Procedure:
Prepare:
Ensure the master cylinder is full of fresh brake fluid.
Begin with the wheel farthest from the master cylinder
(usually the right rear).
Attach Bleeder Hose:
Attach one end of the clear tubing to the bleeder screw
on the wheel cylinder or caliper.
Place the other end of the tubing into a catch container
partially filled with brake fluid.
Pump and Hold:
Have an assistant slowly pump the brake pedal several
times and hold it down.
Open Bleeder Screw:
While the pedal is held down, slowly open the bleeder
screw.
Air and fluid will flow through the tubing into the container.
Close Bleeder Screw:
Before the pedal reaches the floor, close the bleeder
screw.
Release Pedal:
Have the assistant slowly release the brake pedal.
Repeat:
Repeat steps 4-7 until no air bubbles are visible in the
tubing.
Check Fluid Level:
Regularly check the master cylinder fluid level and top it
off as needed.
Move to Next Wheel:
Move to the next wheel, working your way closer to the
master cylinder (left rear, right front, left front).
Final Check:
After bleeding all wheels, check the brake pedal for
firmness.
Ensure the master cylinder is filled to the correct level.
Test drive the vehicle in a safe location to ensure proper
brake operation.
ABS systems:
Some ABS systems require special scan tools to bleed
the system properly.
Identifying Major Steering and Suspension Components
Steering Box (or Steering Rack):
Visual:
Steering Box: A metal housing typically found on older or heavy
duty vehicles, located near the front of the vehicle's frame.
Steering Rack: A long, horizontal metal component found in
most modern vehicles, located behind the engine or in front of
the front axle.
Function: Converts the rotational motion of the steering wheel into the
linear motion required to turn the wheels.
Types:
Recirculating ball steering box.
Rack and pinion steering rack.
Steering Pump (Power Steering Pump):
Visual: A small, belt-driven pump typically mounted on the engine, with
hoses connected to it.
Function: Provides hydraulic pressure to assist in steering, making it
easier to turn the steering wheel.
Components: Reservoir for power steering fluid, pump mechanism,
and pressure hoses.
Dampers (Shock Absorbers or Struts):
Visual: Cylindrical components located near each wheel, connecting
the vehicle's frame or body to the suspension components.
Function: Control the movement of the suspension, absorbing shocks
and vibrations to provide a smooth ride and maintain tire contact with
the road.
Types:
Shock absorbers (separate from the spring).
Struts (integrated with the spring).
Wheel Assembly:
Visual: The complete assembly at each corner of the vehicle,
consisting of:
Wheel (rim): The metal structure that supports the tire.
Tire: The rubber component that provides traction.
Valve Stem: Allows for inflation and deflation of the tire.
Wheel Hub: The central part of the wheel that connects to the
vehicle's axle.
Wheel Bearings: Allow the wheel to rotate smoothly on the hub.
Wheel studs or bolts: used to mount the wheel to the hub.
Function: Provides a means of supporting the vehicle and enabling it
to move.
Components within the wheel assembly:
Wheel bearings: allow the wheel to rotate smoothly.
Brake rotors or drums: part of the braking system.
Wheel studs or bolts: secure the wheel to the hub.
Changing Power Steering Fluid
Changing the power steering fluid is essential for maintaining smooth steering
operation and preventing damage to the power steering pump. Here's a general
procedure:
Tools and Materials:
New power steering fluid (correct type)
Turkey baster or syringe
Wrenches or sockets (appropriate sizes)
Drain pan
Rags or shop towels
Jack and jack stands (optional)
Procedure:
Prepare the Vehicle:
Park the vehicle on a level surface.
Engage the parking brake.
If possible, raise the front of the vehicle using a jack and jack
stands to make it easier to access the power steering reservoir.
Locate the Power Steering Reservoir:
The reservoir is usually a plastic container with a cap marked
"Power Steering."
Consult your vehicle's service manual for the exact location.
Remove Old Fluid:
Use a turkey baster or syringe to remove as much of the old
fluid as possible from the reservoir.
Dispose of the used fluid properly.
Refill with New Fluid:
Fill the reservoir with fresh power steering fluid to the "MAX"
line.
Cycle the System:
Start the engine and let it idle.
Slowly turn the steering wheel from lock to lock several times.
This will circulate the new fluid through the system.
Check Fluid Level:
Turn off the engine and check the fluid level again.
Add more fluid if necessary to reach the "MAX" line.
Check for Leaks:
Inspect the power steering pump, hoses, and reservoir for any
leaks.
Repeat (Optional):
For a more thorough fluid change, you can repeat steps 3-6.
Some vehicles have a drain plug on the power steering rack,
that can be used to more fully drain the system.
Common Faults in Steering and Suspension
Steering:
Power Steering Fluid Leaks: Low fluid levels can cause hard
steering, noise, and pump damage.
Worn Tie Rods: Cause loose steering, wandering, and tire wear.
Worn Ball Joints: Result in clunking noises, loose steering, and tire
wear.
Steering Rack or Box Problems: Can cause hard steering, noise,
and play in the steering wheel.
Power Steering Pump Failure: Leads to hard steering or no power
assist.
Misalignment: Causes uneven tire wear and pulling to one side.
Uneven tire pressure: causes pulling to one side.
Worn Universal joints in the steering shaft: causes play in the
steering wheel.
Suspension:
Worn Shocks or Struts: Cause a bouncy ride, poor handling, and tire
wear.
Worn Springs: Result in a sagging ride height and poor handling.
Worn Control Arm Bushings: Cause clunking noises, loose handling,
and tire wear.
Worn Sway Bar Links or Bushings: Lead to clunking noises and
poor handling during turns.
Worn Wheel Bearings: Cause rumbling or grinding noises and wheel
play.
Broken Springs: Cause a sagging ride height, and a very rough ride.
Air suspension problems: Leaks, compressor failures, or sensor
problems.
Leaking seals in the dampers: result in poor ride quality.
Lubrication Requirements of the Suspension
System
General Principles:
Many modern vehicles use sealed suspension components that are
pre-lubricated and do not require periodic maintenance.
Older vehicles or heavy-duty applications often have grease fittings
(zerks) that allow for manual lubrication.
Using the correct type of grease is crucial. Lithium-based grease is
commonly used for suspension components.
Over-greasing can damage seals, so follow the manufacturer's
recommendations.
Ball Joints:
Function: Ball joints connect the control arms to the steering knuckles,
allowing for movement in multiple directions.
Lubrication:
If equipped with grease fittings, use a grease gun to apply
grease until the old grease is purged and fresh grease is visible.
Rotate the steering wheel while greasing to ensure even
distribution.
Inspect the dust boots for damage. Torn boots allow
contaminants to enter and cause premature wear.
If the ball joint is a sealed unit, replacement is required when the
ball joint has play, or the boot is damaged.
Frequency: Follow the vehicle manufacturer's recommended service
intervals.
Signs of needing lubrication/replacement: Clunking noises during
turns, loose steering, uneven tire wear.
Tie-Rod Ends:
Function: Tie-rod ends connect the steering rack or steering box to the
steering knuckles, transmitting steering input to the wheels.
Lubrication:
Similar to ball joints, tie-rod ends may have grease fittings.
Apply grease using a grease gun, purging the old grease and
inspecting dust boots.
If the tie rod end is sealed, replacement is required when the tie
rod end has play, or the boot is damaged.
Frequency: Follow the vehicle manufacturer's recommended service
intervals.
Wheel (Rim): The metal structure that supports the tire.
Tire: The rubber component that provides traction, cushioning,
and load support.
Valve Stem: Allows for inflation and deflation of the tire.
Wheel Hub: The central part of the wheel that connects to the
vehicle's axle.
Wheel Bearings: Allow the wheel to rotate smoothly on the hub.
Wheel studs or bolts: used to mount the wheel to the hub.
The wheel assembly plays a crucial role in vehicle handling, stability,
and safety.
Common Faults:
Tire-Related:
Punctures or cuts.
Uneven wear (due to misalignment, improper inflation, or
suspension problems).
Bulges or sidewall damage.
Low tire pressure (can lead to poor handling and increased fuel
consumption).
Overinflated tires (can lead to poor traction and a harsh ride).
Worn tread.
Wheel-Related:
Bent or damaged rims (due to impacts).
Loose wheel nuts or bolts.
Damaged valve stems (causing air leaks).
Worn wheel bearings (causing noise and vibration).
Wheel imbalance (causing vibration).
Wheel bearing related:
grinding or rumbling noises.
excessive wheel play.
Removal and Replacement of the Wheel Assembly:
Tools and Materials:
Lug wrench or socket wrench.
Jack and jack stands.
Wheel chocks.
Torque wrench.
Replacement wheel assembly if needed.
Procedure:
Safety First:
Park the vehicle on a level surface.
Engage the parking brake.
Place wheel chocks behind the wheels that are not being
worked on.
Loosen Lug Nuts/Bolts:
Before jacking up the vehicle, use the lug wrench to
loosen the lug nuts or bolts. Turn them counterclockwise.
Do not remove them completely at this stage.
Jack Up the Vehicle:
Position the jack under the vehicle's jacking point, as
specified in the owner's manual.
Raise the vehicle until the wheel is off the ground.
Place a jack stand under the vehicle for added safety.
Lower the vehicle onto the jack stand.
Remove the Wheel:
Remove the lug nuts or bolts completely and carefully
remove the wheel assembly.
Inspection:
Inspect the wheel hub, wheel bearings, and brake
components.
Inspect the tire for damage.
Install the Replacement Wheel (if applicable):
Carefully position the replacement wheel assembly onto
the hub.
Install the lug nuts or bolts by hand, tightening them in a
star pattern.
Lower the Vehicle:
Raise the vehicle slightly to remove the jack stand.
Carefully lower the vehicle to the ground.
Tighten Lug Nuts/Bolts:
Use a torque wrench to tighten the lug nuts or bolts to the
manufacturer's specified torque. Tighten them in a star
pattern.
Final Check:
Ensure all lug nuts or bolts are properly tightened.
