When pushed, spring brake control valves supply air and release the spring brakes. Although, this is the case in most vehicles, sometimes this function works in reverse. Check the description near the control valve to be sure.
The characteristic of older vehicles is that the parking brake control by a lever, that allows you to engage parking brake whenever the vehicle is parked. Also, some trucks have a separate control called a tractor parking-brake control valve.
CDL Air Brakes Tests – Questions and Answers
Here are some questions and answers from the CDL Air Brake Tests I’ve found on Trucker Country:
- If your vehicle has an alcohol evaporator, every day during cold weather you should: Check and fill the alcohol level
- During normal driving, spring brakes are usually held back by: Air pressure
- Air braking takes more time than hydraulic braking because air brakes: Need to have airflow through the lines to work.
- In air brake vehicles, the parking brakes should be used: Whenever the vehicle is parked.
- The brake pedal in an air brake system: Controls the air pressure applied to put on the brakes.
- If your truck or bus has dual parking control valves it means that you can use pressure from a separate tank to: Release the spring brakes to move a short distance.
- A straight truck or bus air brake system should not leak at a rate of more than 2 PSI per minute with the engine off and the brakes released.
- If your vehicle has an alcohol evaporator, it is there to: Reduce the risk of ice in air brake valves in cold weather.
- If you must make an emergency stop, you should brake so that you: Stay in a straight line and can steer.
- Your truck or bus has a dual air brake system. If a low air pressure warning comes on for only one system, what should you do? Stop. Safely park, and continue only after the system is fixed.
Final words
Instead of making conclusions, I will highlight some important things about spring brakes, that driver should be aware of.
