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Brake Systems Flashcards

7 cards from real DTC 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

  1. Under the CVSA out-of-service criteria, what share of a vehicle's service brakes found defective or out of adjustment puts the vehicle out of service?

    Answer: 20% or more

    Under the CVSA 20 percent criterion, a vehicle goes out of service when defective brakes reach 20% or more of its service brakes.

  2. What does a pressure protection valve do in an air brake system?

    Answer: It keeps air in the brake reservoirs by closing an accessory circuit when pressure falls below its set point

    Pressure protection valves close off non-brake accessories so a leak there cannot drain air the brakes need.

  3. An air disc brake has uneven inboard/outboard pad wear and the caliper fails to release fully. What is the most likely cause?

    Answer: Seized or binding caliper guide pins

    Binding guide pins stop the caliper from floating, which causes uneven pad wear and drag.

  4. A trailer built after March 1, 1998 (through 2009) has its ABS warning lamp lit after power-up. Where is that external lamp usually mounted?

    Answer: On the left rear side of the trailer

    Federal rules called for an external trailer ABS lamp on the left side near the rear so the driver can see it in the mirror.

  5. What does the governor do when system pressure reaches cut-out pressure?

    Answer: It sends air to the compressor unloader mechanism so the compressor stops pumping

    At cut-out the governor pressurizes the unloader, which puts the compressor in its unloaded cycle until cut-in.

  6. In a typical hydraulic drum brake system, what is the main job of the residual check valve in the master cylinder outlet?

    Answer: To keep a slight pressure in the lines so wheel cylinder cups stay sealed and air stays out

    A small residual pressure keeps the wheel cylinder cup lips seated and helps keep air out of the system.

  7. After a full service brake application, applied air leakage on a combination vehicle should not go above what rate?

    Answer: 4 psi per minute

    Applied leakage limits are 3 psi per minute for a single vehicle and 4 psi per minute for a combination vehicle.