E - Air Brake System Testing and Service

Question 1

List nine safety precautions that must be observed when working around air brake equipped vehicles.

Answer 1

Park vehicle on a level surface with wheels blocked.
Always wear safety glasses.
Exercise care when working around a running engine.
Drain air from the system prior to service.
Never disconnect lines or remove components when the system is pressurized.
Never adjust system pressure above manufacturer specifications.
Use caution when working around spring brakes.
Understand the air brake system you are working on.
Avoid inhaling dust from brake linings.

Question 2

When visually inspecting the compressor mounting security look for:

Answer 2

Cracked or damaged mounting brackets and loose or missing fasteners.

Question 3

A properly adjusted compressor drive belt will have a maximum deflection of:

Answer 3

1/2 to 3/4 inch (12.70 to 19.05 mm)

Question 4

If you discover excessive oil when draining the air reservoirs, the problem is likely:

Answer 4

Worn air compressor piston rings and cylinders.

Question 5

CVIP specifications state that a vehicle could be put out of service if the brake chamber pushrod travel does not fall between:

Answer 5

3/4 and 1 1/2 inch.

Question 6

When performing the air brake system governor cut-out, pressure warning and pressure buildup test, you found that the low-pressure warning device went off at 70 psi (483 kPa). This means that the operation of the device is:

Answer 6

Acceptable.

Question 7

The Alberta CVIP states that the vehicle compressor should build up from … to … within 3 minutes.

Answer 7

The Alberta CVIP states that the vehicle compressor should build up from 50 psi (345 kPA) to 90 psi (621 kPa) within three minutes.

Question 8

You are testing a vehicle with a governor cut-out pressure of 120 psi (827 kPa) and find that the governor cut-in pressureis 90 psi (621 kPa). The problem is a:

Answer 8

Faulty governor.

Question 9

You are checking for supply circuit leakage in a tandem gravel truck that is towing a pup trailer. The primary service reservoir pressure drops 4 psi (28 kPA) and the secondary reservoir drops 10 psi (69 kPa) over a two minute period. You conclude that:

Answer 9

Primary leakage is acceptable, but secondary leakage is excessive.

Question 10

A body-loaded truck showed a pressure drop of 6 psi (41 kPa) in the primary reservoir and 2 psi (14 kPa) in the secondary reservoir when the service delivery circuit was tested for leakage. You conclude that:

Answer 10

Primary leakage is excessive, but secondary leakage is acceptable.

Question 11

Pushrod travel for a properly adjusted cam-operated foundation brake should be:

Answer 11

As short as possible without drag between the brake linings and drum.

Question 12

The angle formed between the brake chamber pushrod and the slack adjuster arm when the brakes are applied should be:

Answer 12

Never less than 90 degrees.

Question 13

When performing an automatic emergency brake circuit test, you found that the primary air reservoir pressure dropped when the secondary air reservoir was drained. The most probable cause of this fault would be a leak in the:

Answer 13

Check valve in the primary reservoir.

Question 14

Dented or kinked air lines in the parking/emergency brake circuit could cause the spring brakes to:

Answer 14

Be sluggish when applied and released.

Question 15

Opening the supply line of a fully charged tractor/trailer combination with the parking brakes released should cause the trailer brakes to … and the trailer supply valve to …

Answer 15

Immediately apply, shut off air to the supply line between 60 psi (414 kPa) and 20 psi (138 kPa).

Question 16

Before you attempt to mechanically cage spring brakes, you should:

Answer 16

Inspect the spring brake chamber for damage.

Question 17

Before you back off the brakes on units that have automatic slack adjusters, you must be sure to:

Answer 17

Remove and disengage the adjustment pawl.

Question 18

Alberta CVIP states that a vehicle will fail inspection if the radial clearance between the camshaft and bushings is:

Answer 18

0.085 inch (2.16 mm).

Question 19

Camshaft axial play should not exceed:

Answer 19

0.030 inch (0.76 mm)

Question 20

Removing material from the inside diameter of a brake drum results in … and …?

Answer 20

Reduced strength, reduced ability to dissipate heat.

Question 21

Alberta CVIP states that an air brake equipped vehicle will be put out of service if the brake linings are worn below:

Answer 21

5/16 inch (8 mm).

Question 22

Camshaft axial play is adjusted by:

Answer 22

Adding or removing shims between the slack adjuster and its retaining snap ring.

Question 23

If the angle between the brake chamber pushrod and slack adjuster arm is incorrect, you must:

Answer 23

Adjust the brake chamber clevis.

Question 24

It is important to closely watch brake adjustment following a brake reline because:

Answer 24

Brake chamber pushrod travel will increase more rapidly than normal as the brake linings wear in to the brake drums.