CDL air brakes practice test 6

B: There is a mechanical problem with the adjuster or related foundation brake parts, or the adjuster was installed wrong. Pushrod stroke beyond the legal limit on an automatic adjuster points to a mechanical problem in the adjuster or related foundation brake parts, or improper installation. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.

C: Take the vehicle to a repair facility as soon as possible to have the problem corrected. The recommended fix is to get the vehicle to a repair shop promptly. Re-adjusting an automatic adjuster by hand usually hides the underlying fault instead of curing it. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.

C: It may give the driver a false sense of security about the brakes. Manual adjustment of an automatic adjuster usually doesn't fix the underlying problem and may give a false sense of security. Use it only as a temporary measure in an emergency. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.

B: One half the width of the friction area. A crack in a drum or disc is not acceptable if it runs more than half the width of the friction area. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.

D: Linings that are loose or soaked with oil or grease. Linings must not be loose, soaked with oil or grease, or dangerously thin. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.

B: That they aren't cut or worn from rubbing. Look over the hoses going to each brake chamber for cuts or wear caused by rubbing. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.

D: With the engine idling, step on and off the brake to reduce tank pressure and see where the compressor cuts in. With the engine idling, fan the brake pedal to bleed tank pressure down. The compressor should kick back in near the maker's cut-in pressure, and the gauge should start climbing again. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-6.

A: A fast idle. Run the engine at a fast idle. The governor should cut out the compressor at about the manufacturer's specified pressure, and the gauge will stop rising. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-6.

A: It may not keep enough air pressure for safe driving. A governor that doesn't work properly may not keep enough air pressure for safe driving, so it may need to be fixed. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-6.

B: 2 psi in one minute. With the brakes released, the loss rate should be less than 2 psi in one minute for single vehicles (less than 3 psi for combination vehicles). Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-6.

B: 3 psi. The manual's static leakage limit is less than 3 psi in one minute for combination vehicles (less than 2 psi for single vehicles). Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-6.

C: More than 3 psi. If pressure falls more than 3 psi in one minute for a single vehicle (more than 4 psi for a combination), the air loss rate is too much. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-6.

C: 4 psi. For combination vehicles, losing more than 4 psi in one minute with the foot brake fully applied is too much. Find and fix the leaks before driving. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.

C: With the engine off and electrical power on, step on and off the brake pedal to lower tank pressure; the warning must come on before pressure drops below 55 psi. Shut off the engine with enough pressure that the warning is off, turn the electrical power on, and fan the brake pedal. The warning must come on before pressure in the tank (or the lowest tank in a dual system) drops below 55 psi. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.

D: At the manufacturer's specification, within about 20-45 psi. Keep fanning the pedal to lower tank pressure. The parking brake valve should close (pop out) at the manufacturer's specification, within 20-45 psi, and the spring brakes come on. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.

A: Both the tractor protection valve and the parking brake valve. On a tractor-trailer combination, the tractor protection valve and the parking brake valve should both close (pop out), which makes the spring brakes come on. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.

B: From 85 to 100 psi within 45 seconds. In dual air systems, pressure should build from 85 to 100 psi within 45 seconds at operating rpm. Larger-than-minimum tanks can take longer and still be safe; check the manufacturer's specifications. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.

A: 50 to 90 psi within 3 minutes at an idle of 600-900 rpm. In single air systems (pre-1975), a typical requirement is building from 50 to 90 psi within 3 minutes with the engine idling at 600-900 rpm. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.

A: Wait for normal pressure, release the parking brake, move forward slowly (about 5 mph), and brake firmly with the pedal. Wait for normal air pressure, release the parking brake, move forward slowly (about five mph), and apply the brakes firmly with the pedal. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.

A: The vehicle pulling to one side, an unusual feel, or delayed stopping. Watch for the vehicle pulling to one side, a strange pedal feel, or slow stopping. This low-speed test catches problems before you need the brakes in traffic. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.

C: Not until the engine rpm is down close to idle. Brake smoothly, and keep the clutch out until engine speed has dropped to near idle. Then choose a starting gear once stopped. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.1 Normal Stops, page 5-8.

A: You should be able to steer around an obstacle while braking and avoid skids from over-braking. ABS may or may not shorten the stop, but it keeps the wheels rolling, so you can still steer around an obstacle while braking and avoid skids from too much braking. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.2 Braking with Antilock Brakes, page 5-8.

D: The same way you always have, using only the braking force needed to stop safely and stay in control. Brake as you always have: use only the braking force needed to stop safely and stay in control, and brake the same way whether ABS is on the tractor, the trailer, or both. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.2 Braking with Antilock Brakes, page 5-8.

A: Drive normally, since you still have regular brakes, but get the ABS serviced soon. A failed ABS leaves the normal brakes working, so keep driving normally but have the ABS repaired soon. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.2 Braking with Antilock Brakes, page 5-8.