On a hydraulic assisted brake system, what are the forms of power-assisted brake failure backup systems?
To quickly check a hydro-boost power assist unit, put your foot on the brake pedal and start the engine. The pedal should:
A customer complains that his vehicle is equipped with power assist brakes but the pedal now feels hard and there is no assist. What could the problem be?
A truck with a hydro-vac brake booster requires excessive brake pedal effort. Technician A says the one-way check valve may be restricted in the vacuum hose to the hydro-vac unit. Technician B says a sticking power piston in the hydro-vac unit could be the cause. Who is right?
Technician A says that power assist can be found on hydraulically actuated brake systems. Technician B says that one finds power assist on air-over-hydraulic systems. Who is right?
A hydro-vac power assist unit:
A hydro-max power brake booster is being checked. Technician A says that if normal flow from the engine driven hydraulic pump is interrupted, an electric motor and pump provides power for emergency stops. Technician B says manual braking is possible if the power and reserve systems fail, but the braking will be very hard and difficult. Who is right?
Technician A says that when performing a brake overhaul on a hydraulic rear drum brake system, it is good practice to thoroughly inspect and replace any worn springs or retainers. Technician B says the maximum allowable out-of-round specification on a brake drum should be 0.025 inch. Who is right?
On a truck equipped with disc/drum brakes, the front brakes grab quickly when light pedal pressure is applied. This could be caused by a bad:
A hydraulic brake system with a metering valve is being bled. Technician A applies a device to hold the metering valve open when he uses a pressure bleeder to bleed the system. Technician B bleeds the brakes manually with no problems. Who is right?
While discussing hydraulic brake equipped vehicles, Technician A says that vacuum-operated power brake boosters are commonly used on diesel engine heavy duty trucks. Technician B says that hydraulic-operated boosters are commonly used on diesel engine heavy duty trucks. Who is right?
What action would occur if the reserve electrical motor for the hydraulic power brake system failed?
The drag on a truck''s drum brakes increases after each application until they lock up. Bleeding the system restores normal operation for a short time; then the drag increases until the brakes lock up again. Which of these could be the cause?
Which of the following procedures is correct when pressure bleeding a hydraulic brake system?
When discussing wedge brake diagnosis and service, Technician A says installing a new wedge with a different angle does not affect brake operation. Technician B says lubricant should be used on the wedge or wedge ramps. Who is right?
You are inspecting a four-wheel disc hydraulic brake system. Technician A says seized caliper pistons may cause brake drag. Technician B says that rotors machined beyond the minimum diameter may cause brake pedal fade when you first apply the brakes. Who is right?
If a technician fails to install a master cylinder reservoir cover diaphragm, which of the following will it cause?
While road testing a truck after a master cylinder overhaul, the truck brakes seem to drag and overheat. Technician A says that the master cylinder compensation ports may be blocked. Technician B says that excessive spring tension in the residual valve could be the cause. Who is right?
Which of the following conditions can cause brake pedal fade?
Technician A says it is proper to machine worn brake drums, to the manufacturer''s recommendations. Technician B says that turning a drum beyond the manufacturer''s recommendations does not sacrifice its strength. Who is right?
Technician A says that it is good practice to change the hydraulic brake fluid whenever you perform a major brake repair. Technician B says you should immediately replace suspected contaminated hydraulic brake fluid. Who is right?
Technician A says that a hydraulic brake booster and power steering gear can be integrated with the power steering pump. Technician B says that a dedicated hydraulic power source, not connected to the steering gear, can be used to power a hydraulic brake booster. Who is right?
The first part to wear out and need replacing on a duo-servo hydraulic braking system is usually the:
The dash brake warning light in a brake system which uses a dual master cylinder, operates:
The need for brake adjustment is generally indicated by:
A customer complains that he must pump his brake pedal twice in the morning to attain proper pedal height, for the rest of the day when operating the vehicle every few hours he has no problem. What might be the cause of this malfunction occurring every morning?
A customer complains that his disc brake equipped vehicle seems to pull or drift to the right after he applies and releases the brakes and tries to drive on. Which of the following might cause the problem?
Where would a residual check be located, when the vehicle is equipped with a hydro-vac?
A truck with hydraulic disc/drum brakes makes severe hard brake application and experiences brake fade, but does not experience brake fade on repetitive light brake applications. Technician A says this could be caused by an improperly adjusted proportioning valve. Technician B says brake drums worn or machined beyond the maximum diameter could cause this condition. Who is right?
Technician A says that it is friction built up in or on the drum/rotor that causes a vehicle''s forward motion to stop. Technician b says it is the friction of the tires to the road that actually stop a vehicle''s motion. Who is right?
A truck with a hydraulic braking system is being overhauled. Technician A uses a vacuum gauge to test master cylinder output. Technician B says that all the wheel cylinder must be inspected, reconditioned, or replaced when an overhaul is being performed. Who is right?
Technician A says that double flaring can be used on steel brake lines. Technician B says that ISO flaring can be used on steel brake lines. Who is right?
A wheel''s hydraulic brake slave cylinder:
What should be used for the final cleaning of hydraulic brake system parts?
Never use brake fluid out of a used or pre-opened container:
Technician A says that a hydraulic disc brake caliper can have two pistons. Technician B says that a hydraulic disc brake caliper can have one, two, or four pistons. Who is right?
Hydraulic single piston disc brake systems are said to have:
Technician A says that on brakes with vented rotors, the inboard pad could be thicker than the outboard pad. Technician B says that on brakes with solid rotors, the inboard and outboard pads could be the same thickness. Who is right?
What is the difference between a fixed caliper and a sliding caliper?
If the floating caliper on a hydraulic brake truck does not slide freely, which of these conditions will result?
The purpose of the residual check valve in a hydraulic brake system is to:
What is the purpose of a metering valve in a hydraulic brake system?
The purpose of the residual check valve in the master cylinder is to:
Disc type brakes systems:
The brake warning light on the instrument panel, lights up when the brake pedal is depressed, but goes out when the pedal is released. Technician A says that it indicates the brake system has a malfunction. Technician B says that when this happens, it shows that the car is equipped with a self-centering pressure differential switch. Who is right?
A vehicle owner states that the front wheels lock up on a slippery roads, even when braking with light pedal pressure (vehicle has front disc brakes, rear drum brakes). The most probable cause of this problem is a defective:
A vehicle owner states that the rear wheels lock and slide when attempting to bring the vehicle to a fast stop from high speeds. The most probable cause of this problem is a defective:
If the power brake booster has a vacuum leak, all of the following problems would be true except:
The three-way combination valve performs the same functions as the pressure differential switch , metering valve and proportioning valve.
A typical hydraulic power back-up booster interfaces with the following electrical and mechanical components EXCEPT:
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