CDL air brakes practice test 2

B: About 125 psi. The governor cuts out the compressor when tank pressure rises to around 125 psi. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.2 Air Compressor Governor, page 5-1.

B: A spring-loaded dash handle that lets you apply the spring brakes gradually. A modulating valve is a spring-loaded dash handle: the further you move it, the harder the spring brakes come on, so you can control them if the service brakes fail. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.15 Parking Brake Controls, page 5-3.

D: The brakes are fading; slow down and use a lower gear. Needing more and more application pressure for the same speed is a sign of brake fade. Reduce speed and shift to a lower gear. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.10 Application Pressure Gauge, page 5-3.

D: A round blue knob or another shape, including a lever. On older vehicles the control may be a round blue knob or another shape, including a lever that swings side to side or up and down. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.8 Parking Brakes, page 5-9.

C: About 100 psi. Cut-in pressure is around 100 psi; at that point the governor lets the compressor start pumping again. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.2 Air Compressor Governor, page 5-1.

C: Releasing the spring brakes so you can move the vehicle in an emergency after main air pressure is lost. The separate tank lets you release the spring brakes so you can move the vehicle in an emergency after main air pressure has been lost. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.15 Parking Brake Controls, page 5-4.

B: In 'normal,' to have normal stopping power. The 'slippery' position cuts front brake pressure by half and reduces stopping power. Front wheel braking is good in all conditions, so keep the control in 'normal.' Commercial Driver's License Manual (CDL Driver's Manual): 5.1.13 Front Brake Limiting Valve, page 5-3.

D: Don't use the parking brakes; use wheel chocks on a level surface and let the brakes cool. Don't use the parking brakes when the brakes are very hot; the heat can damage them. Use wheel chocks on a level surface and let the brakes cool first. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.8 Parking Brakes, page 5-9.

D: The governor. The air compressor governor decides when the compressor pumps air, cutting it out near 125 psi and back in near 100 psi. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.2 Air Compressor Governor, page 5-1.

A: There is only enough air in the separate tank to release the spring brakes a few times. The separate tank holds only enough air to release the spring brakes a few times. Plan each move, or the air may run out and leave you stuck somewhere dangerous. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.15 Parking Brake Controls, page 5-4.

A: The normal air pressure to the front brakes is cut by half. The 'slippery' setting halves the air sent to the front brakes, which cuts the vehicle's overall stopping power. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.13 Front Brake Limiting Valve, page 5-3.

D: They can freeze so the vehicle can't move. Very wet brakes set in freezing temperatures can freeze so the vehicle cannot move. Use wheel chocks instead, or dry the brakes first. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.8 Parking Brakes, page 5-9.

C: Turn it a quarter turn or pull a cable. Manually operated drains are opened by turning a quarter turn or by pulling a cable. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.4 Air Tank Drains, page 5-1.

D: The spring brakes come on again. The release button is spring-loaded in the 'out' position. When you let go of it, the spring brakes come on again. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.15 Parking Brake Controls, page 5-4.

D: No; tests show front-wheel skids from braking are not likely even on ice. Tests have shown that front-wheel skids from braking are not likely even on ice, and front-wheel braking is good under all conditions. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.13 Front Brake Limiting Valve, page 5-3.

C: Never leave it unattended without applying the parking brakes or chocking the wheels. Always set the parking brakes or chock the wheels before leaving the vehicle. Otherwise it could roll away and hurt someone or cause damage. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.8 Parking Brakes, page 5-10.

C: At the end of each day of driving. Manual drains don't empty themselves, so the driver has to drain each tank after every day of driving. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.4 Air Tank Drains, page 5-1.

C: Either the front or the rear brakes won't be working fully, so it will take longer to stop. If one system is very low, either the front or rear brakes won't work fully, so stopping takes longer. Bring the vehicle to a safe stop and have the system fixed. Commercial Driver's License Manual (CDL Driver's Manual): 5.2 Dual Air Brake, page 5-5.

D: Excessive heat from using them too much and not relying on engine braking. Fade and failure come from too much heat, caused by overusing the service brakes instead of letting the engine do part of the braking. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.5 Brake Fading or Failure, page 5-9.

B: Any time you park, except when the brakes are very hot or very wet in freezing temperatures. Use the parking brakes any time you park, except in the cases the manual notes: very hot brakes, or very wet brakes in freezing temperatures. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.8 Parking Brakes, page 5-9.

A: In the first tank the air compressor pumps air to. The safety relief valve sits in the first tank the compressor fills. It vents air to protect the tanks and the rest of the system from excess pressure. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.6 Safety Valve, page 5-2.

A: You could lose your brakes while driving. Check for air leaks and fix them before driving; otherwise you could lose your brakes while driving. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.

B: Chemical changes in the lining that reduce friction, and expansion of the brake drums. Heat causes chemical changes in the lining that reduce friction, and it expands the drums so the shoes must move farther and press with less force. Commercial Driver's License Manual (CDL Driver's Manual): 5.4.5 Brake Fading or Failure, page 5-9.

C: 150 psi. The manual says the safety valve is usually set to open at 150 psi. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.6 Safety Valve, page 5-2.

B: Without it, you could lose air pressure without knowing, which could cause sudden emergency braking. If the warning doesn't work, you could lose air pressure without knowing it, which could cause sudden emergency braking in a single-circuit system. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.