Air Brakes Foundation

The most hazardous element used in the composition of brake lining as far as the mechanic is concerned is:

iron oxide

aluminum oxide

asbestos

shredded copper

Correct! Wrong!

One of the most important reasons air brakes have been chosen over hydraulic brakes in heavy duty vehicles, is that air brake systems are more tolerant to system leaks.

True

False

Correct! Wrong!

The device used for adjusting the brakes on an S-cam, drum type air brake system is the :

brake chamber

"S" cam

slack adjuster

star wheel

Correct! Wrong!

The "S" cam of a foundation brake assembly functions as a:

brake adjuster

brake shoe actuator

brake calliper

brake shoe retainer

Correct! Wrong!

The air compressor for air brake system is usually pressure lubricated by:

its own oil supply

oil injected into the air inlet

periodic greasing

the engine lubricating system

Correct! Wrong!

Spring brakes commonly operate the ________________ to keep the vehicle from moving when parked.

regular service foundation brake assembly

drive shaft type parking brake assembly

special wheel brake assembly

none of the above

Correct! Wrong!

At what pressure is the safety valve on the air system set?

105

125

150

200

Correct! Wrong!

Why should air tanks not be field welded?

There may be alcohol present

It is illegal

Welding may reduce structural strength

All of the above

Correct! Wrong!

What is the imperial measurement used to identify the torque capacity of a slack adjuster?

Feet

Foot pounds

Inch pounds

Inches

Correct! Wrong!

Where might you find desiccant in an air brake system?

Air cleaner

Air dryer

Compressor

Alcohol injector

Correct! Wrong!

The device that controls the air compressor cut-in and cut-out pressure is known as?

Loader

Relay

Governor

Valve

Correct! Wrong!

A factor that affects stopping distances would be:

weight

speed

traction

all of the above

Correct! Wrong!

An ideal air braking system can be defined as:

one in which braking forces are proportional on all axles

one in which the braking pressure reaches each brake actuator simultaneously and at the same pressure level

one in which each axle receives braking force in a sequential manner, starting with the closest axle to the governor.

one in which each wheel receives a graduated braking force over a preset range of the most probable braking conditions.

Correct! Wrong!

What is the angle at the slack adjuster to push-rod when brakes are applied and properly adjusted?

9 deg

90 deg

100 deg

180 deg

Correct! Wrong!

Reservoirs or air tanks must be drained regularly because:

the air supply gets stale

condensed moisture must be removed

it allows the system to relax

it is necessary prior to making a brake adjustment

Correct! Wrong!

When draining accumulated moisture from the air tanks or reservoirs you should:

have the engine running so that compressor will also drain

operate the service brakes while tanks are draining

"crack" the drain cocks just enough to allow the tanks to blow momentaril

leave the drain cocks open until air and moisture are completely drained

Correct! Wrong!

The correct method to adjust cam brakes is to rotate the slack adjuster screw:

with a clockwise rotation of the adjuster screw

so the S-cam is rotating in the direction it would when cylinder is applying the brakes

so the S-cam is rotating clockwise

with a counterclockwise rotation of the adjuster screw

Correct! Wrong!

Technician A says that if the locking collar is defective on a manual slack adjuster the slack adjuster should be replaced. Technician B says that an automatic slack adjuster needs no lubrication due to permanent lubrication. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

You are servicing a piggyback spring brake assembly. Technician A says no attempt should be made to repair or replace any part of the spring brake portion, but that it should be completely replaced as a unit. Technician B says that the spring chamber should be disarmed (manually released) and safely disabled before discarding. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

Technician A says that air brakes may be wedge-actuated. Technician B says that air brakes may be cam-actuated. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

Technician A says that cam-actuated brake systems are still the most common brake system on heavy duty trucks today. Technician B says that air operated disc brakes are becoming more common all the time. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

In the S-cam foundation brake, the final link between the air system and the foundation brake is:

the air chamber piston to the chamber pushrod

the chamber pushrod to the slack adjuster

the slack adjuster to the S-camshaft

the air chamber mounting plate

Correct! Wrong!

Technician A says that one of the factors affecting air timing is the size of the lines. Technician B says that if an incorrect air line (i.e., too small) were installed, then the air brake timing/balance will be affected. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

Technician A says that a slack adjuster must be adjusted so the angle between it and the chamber pushrod is 90 degrees when the brakes are fully applied. Technician B says that the chamber pushrod should be adjusted with the shortest, possible stroke, without dragging the brakes. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

What is a rule that applies equally to almost all air brake systems?

The first sign of moisture in the line indicates that repair is needed.

Air-operated equipment depends on air pressure in only one direction; movement in the opposite direction requires mechanical means.

Because air systems are a closed system, they do not need filters.

Air lines cannot have more than three 90-degree bends per 5-foot section.

Correct! Wrong!

Why should a slack adjuster need adjusting?

Wedge-type brakes by design require frequent adjusting ; otherwise rapid uneven lining wear will ensue.

The proper free stroke is the reason for adjusting drum to lining clearance on cam-type slack-adjusting brake systems.

If pushrod length is too short, the brakes will drag; thus the clevis to pushrod adjustment is critical.

The angle between the brake chamber pushrod and the centerline of the slack adjuster must be 90 degrees with the brakes fully applied.

Correct! Wrong!

What is one of the most important aspects of air compressor preventative maintenance?

The induction of only clean air

Maintain proper water level

Ensure secure mounting of unit

Maintain efficient governor operation

Correct! Wrong!

An airbrake system is being inspected. Technician A says that the cylinder pushrod spring, in combination with the brake shoe return spring, releases the brakes. Technician B says that normally, the clevis threads onto the slack adjuster arm. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

Technician A says that heat cracking of brake drums will cause rapid lining wear. Technician B says that brake drums (over 14 inches in diameter) may be machined 0.125" over normal new diameter safely. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

Technician A says it''s okay to machine drums, as long as the drum''s manufacturer''s recommendation for machining dimensions are followed. Technician B says that turning a drum oversize will sacrifice its strength. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

When installing the clevis between the pushrod and slack adjuster, Technician A says that the clevis should be correctly positioned on the pushrod in order to facilitate proper brake adjustment. Technician B says that the clevis on a brake chamber pushrod is keyed into location. 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 actually stops a vehicle''s motion. Technician B says it is the shoes/pads being applied against the drums/rotors that actually causes the friction that stops a vehicle''s motion. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

A wig -wag (low air warning device) should operate:

between 20-45 PSI

when pressure drops to 60 PSI

when the vehicle is shut off

at air governor cut-in pressure

Correct! Wrong!

The range between air compressor cut-in pressure and cut-out pressure is approximately _____________ P.S.I.

20

45

105

125

Correct! Wrong!

The pushrod stroke is being measured. Technician A says that the applied stroke uses an 80-psi brake application. Technician B says the brakes are adjusted (if needed) to achieve the proper free stroke. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

You are performing an air timing balance test on a combination vehicle. Technician A uses an accurate watch as part of the required equipment. Technician B says that balanced air timing means each axle receives air at the same time and at the same pressure level as needed by the driver. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

Technician A says when wedge brakes are not properly adjusted, it reduces brake advantage and contributes to poor brake performance. Technician B says that a properly adjusted brake is one where the angle between the slack adjuster and the chamber pushrod is 90 degrees when the brakes are applied. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

What is brake compounding?

Reversing gladhand positions on the trailer and tractor lines.

Running the tractor in a bobtail position,

Rapidly releasing the air in the spring brake chamber to allow the brakes to be applied.

Simultaneous application of the service and emergency side of the spring brake chambers.

Correct! Wrong!

When you are adjusting the tension of the compressor drive belt, you notice contact at the bottom of the pulley with the belt, you should:

ensure tension is to original specification level and recheck the belt''s bottom contact surface for excessive wear.

measure the level of deflection at a section of belt that is longest between pulleys.

first, replace the belt, making sure the correct belt is used, and check for pulley wear.

ignore it because some applications require this additional contacting area

Correct! Wrong!

Technician A says that a warning light and buzzer that do not function below 60 psi is caused by a defective bulb. Technician B says that an inaccurate pressure sender can be the cause of a warning light and buzzer that stays on above 60-psi supply pressure. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

New brake linings are being installed on a truck. Technician A says you use the correct procedure to properly re-rivet new linings on. Technician B always greases the platforms on the backing plate before installing new shoes/linings. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

If the compressor pumps and delivers air well but cuts out at too low a pressure, the ________________should be adjusted.

compressor drive belt

safety valve

slack adjusters

governor

Correct! Wrong!

The moisture that accumulates in the air tanks or reservoirs is a result of:

the small amount of coolant that leaks past the compressor

the condensation of moisture from the lubricating oil

the condensation of moisture from the cooling of the compressed air

the small amount of water that is present when driving in the rain

Correct! Wrong!

If compressor build up time is very slow it can be caused by:

a plugged compressor air filter

system leaks

a worn out compressor

all of the above

Correct! Wrong!

A method used to determined whether or not a check valve found between supply and service tanks is functioning properly is to alternately drain the tanks starting with the supply tank.

True

False

Correct! Wrong!

Poor brake adjustment on cam type air brakes is one of the largest single causes of brake related truck accidents.

True

False

Correct! Wrong!

One -way check valves prevent air flow from the supply tank to the service tank.

True

False

Correct! Wrong!

Spring brakes are:

air released and spring applied

air applied and spring released

spring applied and spring released

spring applied or air applied

Correct! Wrong!

The purpose for having more than one reservoir is:

to provide extra space to collect moisture

to provide faster brake application

to provide a larger volume of air

to allow for higher system pressures

Correct! Wrong!

An air brake chamber identified as type 25 has a

diaphragm diameter of 25"

brake chamber circumference of 25"

diaphragm radius of 25 cm

diaphragm effective area of 25 sq. in.

Correct! Wrong!

The most hazardous element used in the composition of brake lining as far as the mechanic is concerned is:

One of the most important reasons air brakes have been chosen over hydraulic brakes in heavy duty vehicles, is that air brake systems are more tolerant to system leaks.

The device used for adjusting the brakes on an S-cam, drum type air brake system is the :

The "S" cam of a foundation brake assembly functions as a:

The air compressor for air brake system is usually pressure lubricated by:

Spring brakes commonly operate the ________________ to keep the vehicle from moving when parked.

At what pressure is the safety valve on the air system set?

Why should air tanks not be field welded?

What is the imperial measurement used to identify the torque capacity of a slack adjuster?

Where might you find desiccant in an air brake system?

The device that controls the air compressor cut-in and cut-out pressure is known as?

A factor that affects stopping distances would be:

An ideal air braking system can be defined as:

What is the angle at the slack adjuster to push-rod when brakes are applied and properly adjusted?

Reservoirs or air tanks must be drained regularly because:

When draining accumulated moisture from the air tanks or reservoirs you should:

The correct method to adjust cam brakes is to rotate the slack adjuster screw:

Technician A says that if the locking collar is defective on a manual slack adjuster the slack adjuster should be replaced. Technician B says that an automatic slack adjuster needs no lubrication due to permanent lubrication. Who is right?

Technician A says that air brakes may be wedge-actuated. Technician B says that air brakes may be cam-actuated. Who is right?

Technician A says that cam-actuated brake systems are still the most common brake system on heavy duty trucks today. Technician B says that air operated disc brakes are becoming more common all the time. Who is right?

In the S-cam foundation brake, the final link between the air system and the foundation brake is:

Technician A says that one of the factors affecting air timing is the size of the lines. Technician B says that if an incorrect air line (i.e., too small) were installed, then the air brake timing/balance will be affected. Who is right?

Technician A says that a slack adjuster must be adjusted so the angle between it and the chamber pushrod is 90 degrees when the brakes are fully applied. Technician B says that the chamber pushrod should be adjusted with the shortest, possible stroke, without dragging the brakes. Who is right?

What is a rule that applies equally to almost all air brake systems?

Why should a slack adjuster need adjusting?

What is one of the most important aspects of air compressor preventative maintenance?

An airbrake system is being inspected. Technician A says that the cylinder pushrod spring, in combination with the brake shoe return spring, releases the brakes. Technician B says that normally, the clevis threads onto the slack adjuster arm. Who is right?

Technician A says that heat cracking of brake drums will cause rapid lining wear. Technician B says that brake drums (over 14 inches in diameter) may be machined 0.125" over normal new diameter safely. Who is right?

Technician A says it''s okay to machine drums, as long as the drum''s manufacturer''s recommendation for machining dimensions are followed. Technician B says that turning a drum oversize will sacrifice its strength. Who is right?

When installing the clevis between the pushrod and slack adjuster, Technician A says that the clevis should be correctly positioned on the pushrod in order to facilitate proper brake adjustment. Technician B says that the clevis on a brake chamber pushrod is keyed into location. Who is right?

Technician A says that it is friction built up in or on the drum/rotor that actually stops a vehicle''s motion. Technician B says it is the shoes/pads being applied against the drums/rotors that actually causes the friction that stops a vehicle''s motion. Who is right?

A wig -wag (low air warning device) should operate:

The range between air compressor cut-in pressure and cut-out pressure is approximately _____________ P.S.I.

The pushrod stroke is being measured. Technician A says that the applied stroke uses an 80-psi brake application. Technician B says the brakes are adjusted (if needed) to achieve the proper free stroke. Who is right?

What is brake compounding?

When you are adjusting the tension of the compressor drive belt, you notice contact at the bottom of the pulley with the belt, you should:

Technician A says that a warning light and buzzer that do not function below 60 psi is caused by a defective bulb. Technician B says that an inaccurate pressure sender can be the cause of a warning light and buzzer that stays on above 60-psi supply pressure. Who is right?

New brake linings are being installed on a truck. Technician A says you use the correct procedure to properly re-rivet new linings on. Technician B always greases the platforms on the backing plate before installing new shoes/linings. Who is right?

If the compressor pumps and delivers air well but cuts out at too low a pressure, the ________________should be adjusted.

The moisture that accumulates in the air tanks or reservoirs is a result of:

If compressor build up time is very slow it can be caused by:

A method used to determined whether or not a check valve found between supply and service tanks is functioning properly is to alternately drain the tanks starting with the supply tank.

Poor brake adjustment on cam type air brakes is one of the largest single causes of brake related truck accidents.

One -way check valves prevent air flow from the supply tank to the service tank.

Spring brakes are:

The purpose for having more than one reservoir is:

An air brake chamber identified as type 25 has a

Success!

Heavy-Duty Mechanic - Trucks & Equipment