Hydraulic Brakes – Assisted

On a hydraulic assisted brake system, what are the forms of power-assisted brake failure backup systems?

Hydroboost and accumulator

Hydroboost and electric motor driven pump

Electric motor driven pump and accumulator

Hydrovac and electric motor driven pump

Correct! Wrong!

To quickly check a hydro-boost power assist unit, put your foot on the brake pedal and start the engine. The pedal should:

go spongy

drop slightly

not change

go to the floor

Correct! Wrong!

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?

Collapsed or blocked vacuum supply hose

Atmospheric inlet is blocked

Stuck vacuum check valve

All of the above

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

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 only

B only

Both A and B

Neither A nor B

Correct! Wrong!

A hydro-vac power assist unit:

can have a dual diaphragm.

is capable of converting hydraulic pressure into mechanical pressure.

is non repairable.

is exchangeable with other booster(s).

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

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:

proportioning valve.

pressure differential valve.

metering valve.

residual check valve.

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

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?

A only

B only

A and B

Neither A nor B

Correct! Wrong!

What action would occur if the reserve electrical motor for the hydraulic power brake system failed?

You will have not have brake assist without the engine running.

There will be no reserve electrical power in case of an electrical failure in the booster.

Fluid circulation in the steering gear will fail.

Braking power will be reduced with the engine running.

Correct! Wrong!

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?

A swollen master cylinder cup.

An open compensation port.

The wrong brake shoes.

A weak brake shoe return spring.

Correct! Wrong!

Which of the following procedures is correct when pressure bleeding a hydraulic brake system?

You bleed the right front caliper or wheel cylinder first.

The pressure bleeder is pressurized to 15 to 20 psi.

If equipped, the metering valve must be closed.

You bleed the left rear caliper or wheel cylinder last.

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

If a technician fails to install a master cylinder reservoir cover diaphragm, which of the following will it cause?

Fluid contamination

Loss of pressure

Seal erosion

Air drawn into the wheel cylinders

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

Which of the following conditions can cause brake pedal fade?

A seized brake caliper piston.

Brake drum machined beyond its limit.

Leakage past the master cylinder cups.

Air in the hydraulic system.

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

The first part to wear out and need replacing on a duo-servo hydraulic braking system is usually the:

wheel cylinders.

brake shoes or pads.

anchor pins.

return springs.

Correct! Wrong!

The dash brake warning light in a brake system which uses a dual master cylinder, operates:

when a hard brake application is made for an emergency stop.

together with the stop light switch when the brakes are applied normally.

when either half of the dual system fails when the brakes are applied.

when the brake lining reaches critical temperatures.

Correct! Wrong!

The need for brake adjustment is generally indicated by:

the master cylinder fluid level.

the stopping distance of the vehicle.

the brake pedal travel.

the firm or spongy brake pedal feel.

Correct! Wrong!

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?

Improper brake adjustment

Plugged master cylinder vent port

Faulty residual check valve

All of the above

Correct! Wrong!

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?

Seized floating caliper on the right side

Seized floating caliper on the left side

A plugged vent port in the master cylinder

A plugged replenishing port in the master cylinder

Correct! Wrong!

Where would a residual check be located, when the vehicle is equipped with a hydro-vac?

At the master cylinder outlet

At the hydro-vac outlet

At the hydro-vac inlet

None of the above

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

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 only

B only

Both A and B

Neither A nor B

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

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 only

B only

Both A and B

Neither A nor B

Correct! Wrong!

A wheel''s hydraulic brake slave cylinder:

does not need any maintenance.

needs to be inspected at an annual PM.

needs to be replaced periodically.

is usually constructed of sintered bronze

Correct! Wrong!

What should be used for the final cleaning of hydraulic brake system parts?

Water

Mineral spirits

Gasoline

Denatured alcohol

Correct! Wrong!

Never use brake fluid out of a used or pre-opened container:

that is made out of glass, tin, or plastic.

that has been tightly sealed while stored.

that may have been contaminated by any other liquid.

that has had brake fluid in it for more than one year.

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

Hydraulic single piston disc brake systems are said to have:

servo section.

non servo section.

energizing action.

action and reaction.

Correct! Wrong!

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?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

What is the difference between a fixed caliper and a sliding caliper?

Fixed calipers are less expensive than a sliding caliper

Sliding or floating calipers are less expensive than fixed calipers

Fixed caliper pads are smaller than sliding caliper pads

Unlike sliding calipers, a fixed caliper has pistons on both sides of a brake calipers

Correct! Wrong!

If the floating caliper on a hydraulic brake truck does not slide freely, which of these conditions will result?

Excessive brake force

Excessive rotor wear

Reduced braking force

The brakes will grab

Correct! Wrong!

The purpose of the residual check valve in a hydraulic brake system is to:

reduce application lag time of drum brakes.

prevent brake fluid from entering the system.

keep the foot pedal from rising all the way to the top when the brakes are out of adjustment.

to provide for extra brake travel when the brakes are out of adjustment.

Correct! Wrong!

What is the purpose of a metering valve in a hydraulic brake system?

To reduce braking effort to the rear wheels

To increase braking effort to the front wheels

To delay front disc application until rear brakes shoes contact drum

To match braking effort of vehicles with four wheel disc brakes

Correct! Wrong!

The purpose of the residual check valve in the master cylinder is to:

make sure all pressure is relieved when brakes released.

keep the master cylinder full at all times.

ensure the brake lines are slightly charged.

retard application of the disc brakes.

Correct! Wrong!

Disc type brakes systems:

do not have residual check valve.

have a residual pressure of 6 to 8 pounds.

have one residual check valve.

have two residual check valves.

Correct! Wrong!

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?

Technician A

Technician B

Both A and B

Neither A nor B

Correct! Wrong!

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:

metering valve.

proportioning valve.

residual pressure valve.

pressure differential valve.

Correct! Wrong!

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:

metering valve.

proportioning valve.

residual valve.

back check valve.

Correct! Wrong!

If the power brake booster has a vacuum leak, all of the following problems would be true except:

rough engine idle.

hissing sound.

pedal pulsation.

hard pedal.

Correct! Wrong!

The three-way combination valve performs the same functions as the pressure differential switch , metering valve and proportioning valve.

True

False

Correct! Wrong!

A typical hydraulic power back-up booster interfaces with the following electrical and mechanical components EXCEPT:

a buzzer and/or light.

drum/drum, disc/drum, or disc/disc foundation brakes.

the vehicle''s electrical wiring.

the alternator.

Correct! Wrong!

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:

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?

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:

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:

Success!

Heavy-Duty Mechanic - Trucks & Equipment