Brake System Service Flashcards

If an incorrectly adjusted booster pushrod blocks the master cylinder compensating (vent) port, what symptom can result?

Answer: Brakes that drag or fail to release as fluid heats and expands

A blocked compensating port traps pressure in the lines, so expanding fluid keeps the brakes applied.

Why should a new or rebuilt master cylinder be bench bled before installation?

Answer: To remove air from the bores so the system can be bled properly on the vehicle

Bench bleeding purges air from the cylinder, which is hard to remove once it is mounted on the vehicle.

For a typical front/rear split system without a manufacturer-specified sequence, which wheel is usually bled first?

Answer: The wheel farthest from the master cylinder

Bleeding generally starts at the wheel with the longest line, usually right rear, and works toward the closest.

Glycol-based brake fluid is described as hygroscopic. What does this mean for service?

Answer: It absorbs moisture over time, lowering its boiling point

Absorbed water lowers the boiling point and promotes corrosion, so fluid should be tested and flushed periodically.

A force of 100 lb is applied to a master cylinder piston with 1 sq in of area. What output force is produced at a caliper piston with 3 sq in of area?

Answer: 300 lb

Pascal's law gives 100 psi throughout the system, and 100 psi × 3 sq in = 300 lb.

What type of lubricant should be used on disc brake caliper slide pins?

Answer: High-temperature silicone or synthetic brake grease approved for rubber parts

Petroleum products swell rubber boots and bushings, so brake-specific high-temp grease is required.

After installing new rotors, why should lug nuts be tightened with a torque wrench in a star pattern?

Answer: To prevent uneven clamping that causes rotor runout and pulsation

Uneven or excessive lug torque can distort the rotor hat and cause lateral runout.