You are checking a truck whose air compressor has its own oil supply. Which extra check belongs in the pre-trip inspection?
Correct answer: Check that compressor's oil level.
A separately lubricated compressor needs its own oil-level check. Engine lubrication does not automatically cover every compressor design.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.1 — Air Compressor, physical PDF page 82 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
During a stationary check, reservoir pressure falls to the manufacturer's cut-in setting. What should a functioning governor allow?
Correct answer: The compressor to resume building reservoir pressure.
Cut-in is the point at which the compressor resumes charging the air reservoirs. Check the actual cut-in and cutoff settings specified for that vehicle.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.2 — Air Compressor Governor, physical PDF page 82 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
Water has accumulated in an air reservoir before a freezing night. What brake-system risk does this create?
Correct answer: Ice can obstruct components and interfere with braking.
Moisture carried in compressed air can collect in the tanks and freeze. Removing contamination helps prevent brake-system failures in cold conditions.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.4 — Air Tank Drains, physical PDF page 82 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
A truck has manual tank drains and no automatic drainage. When should the driver complete the regular draining task described in the manual?
Correct answer: At the end of each driving day.
The manual's daily draining instruction applies to tanks that require manual drainage. Water and oil can accumulate in warm weather too.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.4 — Air Tank Drains, physical PDF page 82 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
The air-system safety relief valve is venting because pressure is excessive. How should the driver treat this finding?
Correct answer: As a fault requiring mechanical attention.
The relief valve protects against excessive pressure; it is not the normal pressure-regulating control. A venting safety valve requires investigation and repair, not disabling.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.6 — Safety Valve, physical PDF page 83 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
A driver repeatedly presses and releases the air-brake pedal for no reason while waiting to depart. What can happen?
Correct answer: Air may be used faster than the compressor replaces it.
Brake releases discharge air, and the compressor must replenish it. Unnecessary repeated applications can deplete the available supply.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.7 — The Brake Pedal, physical PDF page 83 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
In an S-cam drum brake, what is the purpose of the rotating cam at the wheel?
Correct answer: To press the brake shoes outward against the drum.
The S-cam translates linkage movement into shoe contact with the drum. Friction at that contact slows the wheel; the governor and reservoir have different jobs.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.8 — Foundation Brakes: S-cam, physical PDF page 83 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
One gauge shows reservoir pressure; an optional second type rises with pedal force. What does that second type indicate?
Correct answer: Pressure being applied to the brakes.
Supply pressure and application pressure are different measurements. An application gauge indicates the pressure used for braking, not the amount stored in the tanks.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.9–5.1.10 — Supply and Application Pressure Gauges (physical pages 83–84), physical PDF page 84 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
On a spring-brake-equipped truck, what normally keeps the powerful parking-brake springs from applying while driving?
Correct answer: Sufficient air pressure holding the springs back.
Air pressure holds the spring brakes released. Loss or release of that air allows the mechanical springs to apply the brakes.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.14 — Spring Brakes, physical PDF page 84 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
The wheel brakes on a spring-brake truck are out of adjustment. Which braking capability can be affected?
Correct answer: Both normal braking and spring-brake holding power.
Adequate air pressure alone cannot correct a mechanical adjustment defect. The same wheel-brake condition can undermine service and spring-brake effectiveness.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.14 — Spring Brakes, physical PDF page 84 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
A truck lacks a reliable anti-compounding feature. Why should its driver avoid a hard foot-brake application while the spring brakes are applied?
Correct answer: The combined forces can damage the brake mechanism.
Service pressure and spring force can act together. Not every system prevents this compounding, so the driver must use the controls as specified for the vehicle.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.15 — Parking Brake Controls, physical PDF page 84 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
A bus has a separate emergency reservoir that can briefly release applied spring brakes after main-air loss. What should the driver remember?
Correct answer: That reserve permits only a limited number of releases.
A reserve air supply is finite and must be managed carefully during an emergency move. It is not a repair or an unlimited replacement for the main air system.
Source: Kentucky State Police, current-linked 2025 CDL Manual; section 5.1.15 — Parking Brake Controls: Dual Parking Control Valves, physical PDF page 85 (section 5 has a July 2017 footer). Equipment-study guidance, not a claim about current skills-test scoring; follow the vehicle specification and qualified instruction. ↗
