Brake Systems Flashcards
7 cards from real ASE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Brake Systems flashcards as text
With steady foot pressure applied, the brake pedal slowly sinks to the floor, and no external fluid leaks are found. What is the most likely cause?
Answer: Internal leakage past the master cylinder piston cups
When fluid bypasses the master cylinder cups internally, pressure cannot be held, so the pedal sinks without any visible leak.
Which brake fluid is silicone-based and must never be mixed with glycol-based fluids?
Answer: DOT 5
DOT 5 is silicone-based and doesn't mix with the glycol-based DOT 3, DOT 4, and DOT 5.1 fluids.
What is the main purpose of a proportioning valve in a front disc/rear drum brake system?
Answer: To limit rear brake pressure during hard stops to prevent rear wheel lockup
During hard braking, weight shifts forward, so the proportioning valve reduces rear pressure to keep the rear wheels from locking.
When pressure bleeding a system that has a metering valve, what must the technician do?
Answer: Hold the metering valve stem open with a special tool
The metering valve blocks low pressure to the front brakes, so it must be held open for fluid to flow to the front calipers during pressure bleeding.
Technician A says a residual check valve is commonly used in drum brake circuits. Technician B says a residual check valve is required in disc brake circuits to keep the pads against the rotor. Who is correct?
Answer: Technician A only
Residual check valves keep light pressure on drum brake wheel cylinder cups, but they would cause drag in disc brake circuits.
What usually turns on the red brake warning lamp through the pressure differential switch?
Answer: Unequal pressure between the two hydraulic circuits
If one hydraulic circuit loses pressure, the pressure differential switch piston moves and grounds the warning lamp circuit.
Why should a new or rebuilt master cylinder be bench bled before installation?
Answer: To remove air from the bores so you don't have to bleed the whole system for a long time
Bench bleeding removes air from the master cylinder bores, which makes bleeding the system after installation faster and more complete.