Massachusetts CDL DMV Air Brakes 1
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In a dual air brake system, if one of the air systems gets very low on pressure, either the front or rear brakes will not be operating fully. You should bring your vehicle to a safe stop and have the air system repaired.
If a tractor is equipped with an Anti-Lock Braking System (ABS) but the trailer is not, the risk of jackknifing will be reduced and the driver should still be able to maintain steering control. If only the trailer is equipped with ABS, it is less likely that the trailer will swing out to one side.
In a vehicle with a single air brake system, after the engine is at operating rpms, the pressure in the air system should generally build from 50 to 90 psi within three minutes.
If the air pressure warning light or buzzer comes on while you are driving, you should immediately stop and safely park the vehicle. This warning signal indicates that there is a problem in the air brake system that needs to be fixed.
A parking brake should not be used if the vehicle's brakes are very hot from use on a steep downgrade or if the brakes are very wet and temperatures are freezing. Using the parking brake when brakes are hot could cause damage to the brakes, and using the brakes when they are wet in freezing weather may cause the brakes to ice up, rendering the vehicle immobile.
All air tanks on air-braked vehicles must have one-way check valves located between the air compressor and the first reservoir. This prevents air from flowing out in the event of a leak.
Most heavy-duty vehicles use dual air brake systems. A dual system has two separate air brake systems with a single set of controls.
A low air pressure warning signal is required in vehicles with air brakes. The warning light is usually red and may be accompanied by a buzzer.
Anti-Lock Braking Systems (ABS) are compatible with air braking systems. ABS helps maintain control of a vehicle and prevents the wheels from locking up during hard braking on slippery surfaces. ABS can still provide benefits even if is present on only one axle.
The function of an Anti-Lock Braking System (ABS) is to prevent the vehicle's wheels from locking up from hard brake application.
If the low air pressure warning signals activate, it is essential that you bring the vehicle to a safe stop while you are still able to control the brakes.
In a newer vehicle with air brakes, the parking brake is controlled by a diamond-shaped yellow knob. The knob is pulled out to apply the parking brakes and pushed in to release them.
In an air brake system with manually operated drains, the tanks should be drained at the end of each day of driving.
Before driving a vehicle with a dual air brake system, allow time for the air compressor to build up pressure of at least 100 psi in both the primary and secondary systems.
A parking brake should not be used if the vehicle's brakes are very hot from use on a steep downgrade or if the brakes are very wet and temperatures are freezing. Using the parking brake when brakes are hot could cause damage to the brakes, and using the brakes when they are wet in freezing weather may cause the brakes to ice up, rendering the vehicle immobile.
When driving a vehicle with air brakes, if the low air pressure warning light comes on, it is important for you to stop and safely park your vehicle as soon as possible. There may be a leak in the system. Controlled braking will remain possible only as long as there is enough air left in the tanks.
Before driving a vehicle with a dual air system, allow time for the air compressor to build up a minimum pressure of 100 psi in both the primary and secondary systems.
In an air brake system, the first tank that receives compressed air has a safety valve that releases air if the pressure gets too high. It is usually set to open at 150 psi. If the valve must open, there is a fault in the system that should be repaired by a mechanic.
As long as the brakes are properly maintained, using air brakes is a safe and effective method of stopping large, heavy vehicles.
Before driving a vehicle with a dual air brake system, allow time for the air compressor to build up pressure of at least 100 psi in both the primary and secondary systems.
To prevent the build up of oil and water in a vehicle's air tanks, manually operated air tank drains should be used at the end of each day of driving.
The parking brake should be applied every time you park your vehicle.
On a downgrade, the braking effect of the engine should be your primary method of controlling speed. Shift down to a lower gear before starting down the hill and save the brakes for additional slowing or stopping that may be required by road or traffic conditions.
In an air brake system, the air storage tanks must be drained to remove accumulated water and compressor oil. Failing to do so can cause damage. Manually operated drains should be used at the end of each day of driving.
All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes. These brakes must be held by mechanical force.
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