1. Brake System Problem Diagnosis & ABS Service Tips

2. Brake Squeal
is usually the result of high frequency metal-to-metal vibration
on drum brakes…
ensure the 6 brake shoe support pads have a thin coat of high temp lube such as anti-seize compound
on disc brakes…
ensure brake shims are used on the brake pad backings
check abutment clips – replace if needed
clean & lubricate the caliper slides
alternate brake pad composition may help
organic
semi-metallic
ceramic

3. Brake Pedal Pulsation or Steering Wheel Shimmy
front brake rotors need refinishing or replacement
wheel installation with an impact gun can cause this
hard, panic stops when the brakes are hot can lead to these conditions
remember to measure the disc thickness to determine if there is enough material left to machine

4. Low Brake Pedal this is usually caused by either…
1) brake shoes are out of adjustment
(shoes are too far away from drum)
2) air in the hydraulic lines
if this is the case YOU HAVE A BRAKE FLUID LEAK!!!
air in the system is not a normal condition!
brake fluid level should never get below the MIN mark
brake warning lamp may be illuminated
pump the brake pedal rapidly 3 or 4 times
if the pedal came up higher: shoe adjustment issue
if the pedal is still low: air in the line(s)

5. Brakes Pull to One Side
ensure it is not the steering system creating the pull
if it pulls with the brakes off – it is most likely in the steering system & not the brakes
one of the front calipers isn’t working properly
rebuild or replace calipers
restricted front brake flex hose
prevents brake fluid from becoming pressurized
pulling is not the result of metering valve, proportioning valve or ABS problems

6. Dragging Brake(s) can be associated with sluggish vehicle performance
brakes will smell when overheated
can be a caliper piston is not retracting
e-brake cable is not releasing completely
drum brake shoes adjusted too close to the drum
can be caused by a collapsed flex hose
this allows brake fluid to pressurize
but when pedal is released fluid is “trapped” under pressure and piston can’t retract
loosen the bleeder to determine if this is the cause

7. Brakes Grab / Lock-up
if both rear brakes grab, front brakes should be inspected carefully
proportioning valve limits pressure to rear wheels
if front brakes aren’t functioning correctly then rear brakes will have to work harder to stop the vehicle
with the transfer of weight from back to front on hard braking, this can lead to rear wheel lock-up
this is usually the result of oil, grease or brake fluid on the brake linings
replace defective grease seal, wheel cylinder or axle seal

8. Brake Pedal Sinks
you are stopped at a red light & the pedal is at its normal height
slowly, the pedal starts to sink to the floor
you quickly pump up the pedal & it returns to normal height
again it starts to sink
this is caused by…
an internal leak in the master cylinder
fluid is leaking past the primary seal(s)

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Auto Insurance

10. ABS System Service…

11. ABS System Diagram

12. Servicing Precautions
bleeding (removing air from hydraulic lines) & flushing brake fluid
may be done exactly the same as a non-ABS equipped vehicle
or may have specific bleeding procedures which
when disconnecting brake lines, accumulator pressure may have to be relieved – can be up to 2800 PSI!
pumping the brake pedal 30 to 40 times with engine off may be necessary
read manufacturer's instructions carefully before beginning repairs!
ABS problem: always begin with a thorough inspection of the base brake system (non-ABS portion) first
brake warning light indicates a problem in the base braking system – not the ABS
ABS warning lamp indicates a problem within the ABS

13. Warning Lights
both brake warning lights should come on for about 6 seconds when the ignition is initially turned on
this confirms that the warning circuit is operational

14. Service Tips
check wheel speed sensors for debris build-up (permanent magnet)
check sensor wiring & connectors
frayed insulation
incorrect routing can chafe wiring
loose, corroded connectors

15. Service Tips check tone rings for damage/debris build-up
mismatched tire sizes will confuse the EBCM

16. follow manufacturer’s repair procedures carefully…

17. Service Tips
when replacing brake pads, do not push caliper pistons in without loosening bleeder screw
this prevents dirt from being pushed out of the caliper & into the brake modulator & master cylinder
regular brake fluid flushes (every 2 years) will minimize modulator & solenoid problems & extend their life span