| PROBABLE CAUSE |
CORRECTIVE ACTION |
No brakes — pedal travels to floor
|
| 1 Low fluid level |
1 and 2 Low fluid level and air in the system are symptoms of another problem a leak somewhere in the hydraulic system. Locate and repair the leak |
| 2 Air in system |
| 3 Defective seals in master cylinder |
3 Replace master cylinder |
| 4 Fluid overheated and vaporized due to heavy braking |
4 Bleed hydraulic system (temporary fix). Replace brake fluid (proper fix) |
Brake pedal slowly travels to floor under braking or at a stop
|
| 1 Defective seals in master cylinder |
1 Replace master cylinder |
| 2 Leak in a hose, line, caliper or wheel cylinder |
2 Locate and repair leak |
| 3 Air in hydraulic system |
3 Bleed the system, inspect system for a leak |
Brake pedal feels spongy when depressed
|
| 1 Air in hydraulic system |
1 Bleed the system, inspect system for a leak |
| 2 Master cylinder or power booster loose |
2 Tighten fasteners |
| 3 Brake fluid overheated (beginning to boil) |
3 Bleed the system (temporary fix). Replace the brake fluid (proper fix) |
| 4 Deteriorated brake hoses (ballooning under pressure) |
4 Inspect hoses, replace as necessary (it’s a good idea to replace all of them if one hose shows signs of deterioration) |
Brake pedal feels hard when depressed and/or excessive effort required to stop vehicle
|
| 1 Power booster faulty |
1 Replace booster |
| 2 Engine not producing sufficient vacuum, or hose to booster clogged, collapsed or cracked |
2 Check vacuum to booster with a vacuum gauge. Replace hose if cracked or clogged, repair engine if vacuum is extremely low |
| 3 Brake linings contaminated by grease or brake fluid |
3 Locate and repair source of contamination, replace brake pads or shoes |
| 4 Brake linings glazed |
4 Replace brake pads or shoes, check discs and drums for glazing, service as necessary |
| 5 Caliper piston(s) or wheel cylinder(s) binding or frozen |
5 Replace calipers or wheel cylinders |
| 6 Brakes wet |
6 Apply pedal to boil-off water (this should only be a momentary problem) |
| 7 Kinked, clogged or internally split brake hose or line |
7 Inspect lines and hoses, replace as necessary |
Excessive brake pedal travel (but will pump up)
|
| 1 Drum brakes out of adjustment |
1 Adjust brakes |
| 2 Air in hydraulic system |
2 Bleed system, inspect system for a leak |
Excessive brake pedal travel (but will not pump up)
|
| 1 Master cylinder pushrod misadjusted |
1 Adjust pushrod |
| 2 Master cylinder seals defective |
2 Replace master cylinder |
| 3 Brake linings worn out |
3 Inspect brakes, replace pads and/or shoes |
| 4 Hydraulic system leak |
4 Locate and repair leak |
Brake pedal doesn’t return
|
| 1 Brake pedal binding |
1 Inspect pivot bushing and pushrod, repair or lubricate |
| 2 Defective master cylinder |
2 Replace master cylinder |
Brake pedal pulsates during brake application
|
| 1 Brake drums out-of-round |
1 Have drums machined by an automotive machine shop |
| 2 Excessive brake disc runout or disc surfaces out-of-parallel |
2 Have discs machined by an automotive machine shop |
| 3 Loose or worn wheel bearings |
3 Adjust or replace wheel bearings |
| 4 Loose lug nuts |
4 Tighten lug nuts |
Brakes slow to release
|
| 1 Malfunctioning power booster |
1 Replace booster |
| 2 Pedal linkage binding |
2 Inspect pedal pivot bushing and pushrod, repair/lubricate |
| 3 Malfunctioning proportioning valve |
3 Replace proportioning valve |
| 4 Sticking caliper or wheel cylinder |
4 Repair or replace calipers or wheel cylinders |
| 5 Kinked or internally split brake hose |
5 Locate and replace faulty brake hose |
Brakes grab (one or more wheels)
|
| 1 Grease or brake fluid on brake lining |
1 Locate and repair cause of contamination, replace lining |
| 2 Brake lining glazed |
2 Replace lining, deglaze disc or drum |
Vehicle pulls to one side during braking
|
| 1 Grease or brake fluid on brake lining |
1 Locate and repair cause of contamination, replace lining |
| 2 Brake lining glazed |
2 Deglaze or replace lining, deglaze disc or drum |
| 3 Restricted brake line or hose |
3 Repair line or replace hose |
| 4 Tire pressures incorrect |
4 Adjust tire pressures |
| 5 Caliper or wheel cylinder sticking |
5 Repair or replace calipers or wheel cylinders |
| 6 Wheels out of alignment |
6 Have wheels aligned |
| 7 Weak suspension spring |
7 Replace springs |
| 8 Weak or broken shock absorber |
8 Replace shock absorbers |
Brakes drag (indicated by sluggish engine performance or wheels being very hot after driving)
|
| 1 Brake pedal pushrod incorrectly adjusted |
1 Adjust pushrod |
| 2 Master cylinder pushrod (between booster and master cylinder) |
2 Adjust pushrod incorrectly adjusted |
| 3 Obstructed compensating port in master cylinder |
3 Replace master cylinder |
| 4 Master cylinder piston seized in bore |
4 Replace master cylinder |
| 5 Contaminated fluid causing swollen seals throughout system |
5 Flush system, replace all hydraulic components |
| 6 Clogged brake lines or internally split brake hose(s) |
6 Flush hydraulic system, replace defective hose(s) |
| 7 Sticking caliper(s) or wheel cylinder(s) |
7 Replace calipers or wheel cylinders |
| 8 Parking brake not releasing as required |
8 Inspect parking brake linkage and parking brake mechanism, repair as required |
| 9 Improper shoe-to-drum clearance |
9 Adjust brake shoes |
| 10 Faulty proportioning valve |
10 Replace proportioning valve |
Brakes fade (due to excessive heat)
|
| 1 Brake linings excessively worn or glazed |
1 Deglaze or replace brake pads and/or shoes |
| 2 Excessive use of brakes |
2 Downshift into a lower gear, maintain a constant slower speed (going down hills) |
| 3 Vehicle overloaded |
3 Reduce load |
| 4 Brake drums or discs worn too thin |
4 Measure drum diameter and disc thickness, replace drums or discs as required |
| 5 Contaminated brake fluid |
5 Flush system, replace fluid |
| 6 Brakes drag |
6 Repair cause of dragging brakes |
| 7 Driver resting left foot on brake pedal |
7 Don’t ride the brakes |
Brakes noisy (high-pitched squeal)
|
| 1 Glazed lining |
1 Deglaze or replace lining |
| 2 Contaminated lining (brake fluid, grease, etc.) |
2 Repair source of contamination, replace linings |
| 3 Weak or broken brake shoe hold-down or return spring |
3 Replace springs |
| 4 Rivets securing lining to shoe or backing plate loose |
4 Replace shoes or pads |
| 5 Excessive dust buildup on brake linings |
5 Wash brakes off with brake system cleaner |
| 6 Brake drums worn too thin |
6 Measure diameter of drums, replace if necessary |
| 7 Wear indicator on disc brake pads contacting disc |
7 Replace brake pads |
| 8 Anti-squeal shims missing or installed improperly |
8 Install shims correctly |
Brakes noisy (scraping sound)
|
| 1 Brake pads or shoes worn out; rivets, backing plate or brake |
1 Replace linings, have discs and/or drums machined (or replace) shoe metal contacting disc or drum |
Brakes chatter
|
| 1 Worn brake lining |
1 Inspect brakes, replace shoes or pads as necessary |
| 2 Glazed or scored discs or drums |
2 Deglaze discs or drums with sandpaper (if glazing is severe, machining will be required) |
| 3 Drums or discs heat checked |
3 Check discs and/or drums for hard spots, heat checking, etc. Have discs/drums machined or replace them |
| 4 Disc runout or drum out-of-round excessive |
4 Measure disc runout and/or drum out-of-round, have discs or drums machined or replace them |
| 5 Loose or worn wheel bearings |
5 Adjust or replace wheel bearings |
| 6 Loose or bent brake backing plate (drum brakes) |
6 Tighten or replace backing plate |
| 7 Grooves worn in discs or drums |
7 Have discs or drums machined, if within limits (if not, replace them) |
| 8 Brake linings contaminated (brake fluid, grease, etc.) |
8 Locate and repair source of contamination, replace pads or shoes |
| 9 Excessive dust buildup on linings |
9 Wash brakes with brake system cleaner |
| 10 Surface finish on discs or drums too rough after machining |
10 Have discs or drums properly machined (especially on vehicles with sliding calipers) |
| 11 Brake pads or shoes glazed |
11 Deglaze or replace brake pads or shoes |
Brake pads or shoes click
|
| 1 Shoe support pads on brake backing plate grooved or |
1 Replace brake backing plate excessively worn |
| 2 Brake pads loose in caliper |
2 Loose pad retainers or anti-rattle clips |
| 3 Also see items listed under Brakes chatter |
|
Brakes make groaning noise at end of stop
|
| 1 Brake pads and/or shoes worn out |
1 Replace pads and/or shoes |
| 2 Brake linings contaminated (brake fluid, grease, etc.) |
2 Locate and repair cause of contamination, replace brake pads or shoes |
| 3 Brake linings glazed |
3 Deglaze or replace brake pads or shoes |
| 4 Excessive dust buildup on linings |
4 Wash brakes with brake system cleaner |
| 5 Scored or heat-checked discs or drums |
5 Inspect discs/drums, have machined if within limits (if not, replace discs or drums) |
| 6 Broken or missing brake shoe attaching hardware |
6 Inspect drum brakes, replace missing hardware |
Rear brakes lock up under light brake application
|
| 1 Tire pressures too high |
1 Adjust tire pressures |
| 2 Tires excessively worn |
2 Replace tires |
| 3 Defective proportioning valve |
3 Replace proportioning valve |
Brake warning light on instrument panel comes on (or stays on)
|
| 1 Low fluid level in master cylinder reservoir (reservoirs with fluid level sensor) |
1 Add fluid, inspect system for leak, check the thickness of the brake pads and shoes |
| 2 Failure in one half of the hydraulic system |
2 Inspect hydraulic system for a leak |
| 3 Piston in pressure differential warning valve not centered |
3 Center piston by bleeding one circuit or the other (close bleeder valve as soon as the light goes out) |
| 4 Defective pressure differential valve or warning switch |
4 Replace valve or switch |
| 5 Air in the hydraulic system |
5 Bleed the system, check for leaks |
| 6 Brake pads worn out (vehicles with electric wear sensors — small |
6 Replace brake pads (and sensors) probes that fit into the brake pads and ground out on the disc when the pads get thin) |
Disc brakes do not self adjust
|
| 1 Defective caliper piston seals |
1 Replace calipers. Also, possible contaminated fluid causing soft or swollen seals (flush system and fill with new fluid if in doubt) |
| 2 Corroded caliper piston(s) |
2 Same as above |
Drum brakes do not self adjust
|
| 1 Adjuster screw frozen |
1 Remove adjuster, disassemble, clean and lubricate with high-temperature grease |
| 2 Adjuster lever does not contact star wheel or is binding |
2 Inspect drum brakes, assemble correctly or clean or replace parts as required |
| 3 Adjusters mixed up (installed on wrong wheels after brake job) |
3 Reassemble correctly |
| 4 Adjuster cable broken or installed incorrectly (cable-type adjusters) |
4 Install new cable or assemble correctly |
Rapid brake lining wear
|
| 1 Driver resting left foot on brake pedal |
1 Don’t ride the brakes |
| 2 Surface finish on discs or drums too rough |
2 Have discs or drums properly machined |
| 3 Also see Brakes drag |
|
