ASE A5 Exam Study Material - Current Edition Solutions

ASE A5 Exam Study Material - Current Edition Solutions 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 D. reduces pedal pulsation by controlling hydraulic pressure - answer - 4. The correct answer is B. Residual check valve(s) are used on drum brakes to keep residual low pressure (slight static pressure) in the brake system at all times even when the brake pedal is released. This pressure (5-20 psi) keeps the lips of the wheel cylinder piston cups tight against the cylinder walls to prevent air from entering the system when at rest (brakes released). 5. A technician has just overhauled the front brakes on a vehicle with front disc and rear drum brakes. However, when he attaches a pressure bleeder (pressurized to about 25 psi) to the master cylinder, he cannot get any fluid to come out of the disc brake caliper bleeder screws. Which of the following is MOST LIKELY the cause? A. bad proportioning valve B. bad pressure differential valve C. proportioning valve release button not activated D. metering valve release button not activated - answer - 5. The correct answer is D. A metering valve requires a minimum pressure (typically between 75-125 psi) to open. At this point pressurized fluid flows to the front calipers. Since the bleeder tank is only pressurized to 25 psi, fluid pressure is too low to open the metering valve during this procedure. Therefore, when you use a pressure bleeder on a system with a metering valve, you must manually keep the valve open by either pushing the button in on the end of the valve, or pulling the stem outward on the end of the valve. 6. On a vehicle with single piston floating caliper front disc brakes, the brake pads on the left side of the vehicle are almost completely worn while the right side is almost new. Technician A