ASE A5 Brakes VERIFIED SOLUTIONS 2023//2024

1. On a car with disc/drum brakes, the front brakes grab quickly when light pedal pressure is applied. This problem could be caused by a bad: A. proportioning valve B. pressure safety switch C. metering valve D. residual check valve - ANSWER 1. The correct answer is C. The metering valve delays the flow of brake fluid to the front calipers until the pressure in the system rises to a point where the wheel cylinder can overcome the tension of the brake shoe return springs. The purpose is to have both front and rear brakes apply simultaneously. This prevents the front brakes from locking up during light brake applications. 2. The driver of a vehicle with power disc/drum brakes says that the brake pedal moves slowly to the floor while maintaining pedal pressure at a stoplight. What could cause this problem? A. leaking primary piston cup in master cylinder B. leaking power brake booster C. leaking residual check valve in master cylinder D. internal leak in the combination valve - ANSWER 2. The correct answer is A. If the primary piston cup in the master cylinder is leaking, pressure will not build up ahead of the primary piston to increase pressure to the rear brakes. The piston will then move forward until the spring is compressed enough to move the secondary piston. Consequently, this internal leak will cause the brake pedal to slowly drop to the floor. 3. Which of the following would MOST LIKELY happen if the measurements taken from the check shown above varied from the manufacturer's specifications? A. noisy brake operation B. brake grab or pull C. pulsating brake pedal D. low brake pedal - ANSWER 3. The correct answer is C. Poor rotor parallelism (thickness variation) will cause a pulsating brake pedal. This is due to the caliper piston movement that occurs as the pad rides over the alternating high and low areas on the disc. This action forces brake fluid to flow back and forth from the caliper to the master cylinder, creating the pulsating pedal feedback. 4. What is the purpose of the master cylinder residual check valve(s) on vehicles equipped with drum brakes? A. allows the driver to pump up the brakes B. prevents air from entering the hydraulic system C. prevents wheel lockup by reducing the hydraulic pressure