Tech Tips

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Brakes

Brake Hydraulics: Maintenance and Troubleshooting Tips

BRAKES DRAG

1. Bad master cylinder
2. Tapered lining wear caused by improper caliper mounting
3. Residual pressure valve in system where it's not needed, or residual valve with too high pressure
4. System hydraulically locked up by lack of pedal freeplay
5. Weak, deflecting caliper mounting brackets
6. Caliper misaligned at rotor
7. Excessive rotor runout/warped rotors
8. Master cylinder has internal residual pressure valve. Remove valve.

PEDAL TRAVEL TOO DEEP

1. Air trapped in fluid
2. Master cylinder too small
3. Pedal ratio too great
4. Excessive spindle deflection in cornering (causing caliper piston knock-back)
5. Warped rotors
6. Calipers misaligned at rotor

OSCILLATION FEEDBACK (PEDAL BOUNCE)

1. Excessive rotor runout
2. Rotor faces not parallel
3. Cracked rotor
4. Loose or improperly mounted caliper
5. Pad lining buildup (welding) on rotors
6. Excessive front wheel bearing clearance

CAR PULLS DURING BRAKING

1. Contaminated brake pad on one or more calipers
2. Sticking/frozen pistons in one or more calipers
3. Wheel alignment (incorrect camber, caster or toe) Examples: too much negative camber on right front will cause car to pull to the left; too little negative camber on right front will cause car to pull to the right; not enough positive caster on right front wheel will cause car to pull to the right; too much toe-out on right front can cause pull to the right.
   

PEDAL DROPS TO FLOOR DURING USE

1. Fluid boiling (caused by overheat from brake drag; old or inadequate fluid; inadequate air ducting; undersize brake system for application)
2. Master cylinder failure
3. Leak in system (caliper, lines, etc.)
4. Pedal linkage failure
5. Excessive spindle deflection during cornering (causing caliper piston knock-back)
6. Wrong size residual valve

EXCESSIVE PEDAL EFFORT REQUIRED

1. Master cylinder too large
2. Insufficient pedal ratio
3. Caliper piston area too small
4. Contaminated pads (oil, grease, etc.)
5. Caliper pistons stuck/frozen
6. Fade caused by incorrect pad selection (if rotors glow orange, don't use soft pads)
7. Glazed pads/rotors (replace pads with correct type and sand rotors)
8. Pedal mounted at severe angle (master cylinder pushrod should be no more than 5 degrees off-line of pedal and ideally should be in-line)

CALIPER LEAKS

1. Caliper seals old, dried. Replace seals.
2. Nick or other damage on piston, or damaged seal

SPONGY PEDAL

1. Air in brake system
2. Calipers incorrectly mounted with bleed screws not in high location
3. Too-small master cylinder
4. Faulty master cylinder
5. Calipers misaligned to rotor
6. Calipers mounted equal to or higher than master cylinder. Install 2-lb residual valve
7. Excessive caliper flex. Check line pressure, which should not exceed 1500 psi
8. Pedal ratio too great
9. Excessive spindle deflection in corners, causing piston knock-back

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