What is a brake combination valve?
Definition & Description. A Brake Combination Valve is exactly what it sounds like. Its job is to achieve Balanced Braking. Combination valves are often just called “proportioning valves.” However, in reality, they do more. They are usually installed on vehicles with front disc and rear drum brakes.
What is the purpose of combination valve?
Most combination valves perform 3 functions: The Proportioning Valve keeps the rear brakes from locking up during a panic stop. The Metering Valve delays the front brakes long enough for the fluid pressure to overcome the rear brake return springs. A pressure switch sends an electrical signal.
What causes an air brake valve to fail?
AIR BRAKE SYSTEM TROUBLESHOOTING 1.) Before replacing any valve with a new or remanufactured valve, be sure to blow the air lines out either using the vehicle’s own air supply or shop air. Dirt is the greatest cause of premature air valve failure. 2.)
What to do if your brake valve is no longer centered?
If the valve is no longer centered, the process of realigning it is extremely difficult and frustrating. To keep the valve from misaligning, simply replace the switch with the proportioning valve centering tool (bleeder tool) prior to the brake-bleeding process.
What causes a pressure differential valve to become uncentered?
This switch notifies the driver of a loss of brake pressure in either the front or rear brakes. A common problem that occurs when bleeding the brakes is uneven pressure through the brake system. This causes the pressure differential valve to move to the front or rear and become uncentered.
What should I know about my air brake system?
-Brakes need adjusting, lubricating or relining. -Low air pressure in the brake system (below 60 psi). -Brake valve delivery pressure below normal. -Wrong size actuators and/or slack adjusters. -Failure of part of a dual air system. -If remote mounted brake valve, check linkage.
What happens if there is no air pressure in the brake system?
Brakes Do Not Apply -No air pressure in brake system. -Restricted or broken tubing or hose. -Faulty brake valve. If remote mounted brake valve, check linkage. 5.) Brakes Do Not Release -Brake rigging binding. -Brake not in fully released position. -Faulty brake valve or relay valve. -Restricted or collapsed tubing or hose.
How does the brake pressure modulate valve work?
It is a device that is controlled by the electric signal that is generated by the ABS module. The brake pressure modulate valve regulates the pressure that is supplied to each ABS controlled brake in the wheels. The modulate valve has a set of solenoid valves, usually one for each wheel, that are controlled by the ECU.
This switch notifies the driver of a loss of brake pressure in either the front or rear brakes. A common problem that occurs when bleeding the brakes is uneven pressure through the brake system. This causes the pressure differential valve to move to the front or rear and become uncentered.
Which is the key component of a power brake system?
The key element in a power brake system is the brake control valve, sometimes called a brake metering valve. It responds to brake pedal input by directing aircraft system hydraulic fluid to the brakes.