CDL Air Brakes TestAir Brake System PartsHard
A driver observes that when they fully depress the brake pedal, the service brakes are slow to release, causing the vehicle to drag slightly. They verify that the slack adjusters are properly adjusted. What is the most likely cause of this issue?
- AWorn or seized spring brakes.
- BA malfunctioning air compressor governor.
- CRestricted or kinked brake lines to the service brake chambers.
- DA faulty low air pressure warning switch.
Show answer & explanationAnswer & explanation
Correct answer: C. Restricted or kinked brake lines to the service brake chambers.
Slow brake release, despite proper slack adjustment, often indicates that air pressure is not exhausting quickly enough from the brake chambers. Restricted or kinked air lines would impede this exhaust, causing the brakes to drag.
Why the other options are wrong
- A. Worn spring brakes would affect parking brake holding power, not the release of service brakes, which are air-actuated.
- B. The governor affects pressure build-up and cut-out, not brake release speed.
- D. A faulty warning switch affects the dashboard indicator, not the mechanical release of the brakes.
Restricted Brake Lines (Service Brakes)
Air lines to the service brake chambers that are partially blocked or kinked, preventing rapid air flow and causing slow application or release of the service brakes.
- Can cause brakes to drag or apply unevenly.
- Increases stopping distance and brake wear.
- Requires inspection and replacement of affected lines.
- Distinguished from slack adjuster issues by proper adjustment.
Memory trick: Air's stuck, not flowing free, slow release, for all to see.