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Brake proportioning valve is a crucial element of a vehicle’s safety mechanism. In this auto guide, I will cover every detail regarding Brake Proportioning Valve and its reset method.
The braking system of every vehicle consists of a brake proportioning valve that regulates the pressure applied to the rear brakes. It is achieved by maintaining the fluid going to the rear brakes when emergency brakes are applied.
How Does Brake Proportioning Valve Work?
Proportioning valve is usually located on the rear brakes. Whenever sudden brakes are applied, the valve balances the pressure between the rear and front by controlling the fluid flow to the rear brakes.
Due to the car’s aerodynamics, the front brakes require more pressure than the fronts whenever you apply the brakes. The brake proportioning valve manages this pressure difference and provides a more stable performance when you hit the brakes. It prevents the rear wheel from locking that will stop without sliding.
If you are going at high speed and suddenly apply brakes, the rear wheel stops first because it requires less pressure. This increases the chances of slipping or losing control of the vehicle, particularly in rainy or snowy conditions. Brake proportioning valve manages the brake pressure distribution among the wheels, so your car responds better to brakes and stops safely.
Brake proportioning valve is connected to the piston. When the vehicle is running, a spring holds the piston open for the fluid to flow. When you apply brakes, the safety mechanism kicks in, and the valve becomes active. Here is how it works:
- When the brakes are applied, fluid pressure from the master cylinder to the brakes increases rapidly.
- The fluid pressure pushes the spring that’s holding the piston in its place. And the piston moves toward the brakes.
- The valve is closed by the piston movement, which restricts the fluid flow to the rear brakes.
When To Reset Brake Proportioning Valve?
The primary indication of a faulty brake proportioning valve is frequent rear lock-ups. Whenever you apply the brakes, the rear wheels will stop before the front wheels, which means the car will slow down, but the real wheels will stop and start skidding. Not only does it harm your tire wear, but it also increases the chances of losing control of the car, as the wheels are more difficult to turn when locking up.
Furthermore, when you feel the rear brakes getting more sensitive to the touch, it’s time to check the brake proportioning valve.
How to Reset/Adjust Brake Proportioning Valve?
A faulty Brake Proportioning Valve will apply the same amount of pressure to each wheel, which causes rear wheel locking. You can manage the fluid flow to the rear brakes by resetting the valve, so your vehicle stops without the wheels skidding on the surface. Here is how you can do it:
- Find the Brake Proportioning Valve located on the rear brake line.
- Press and hold the Reset button on the valve for a few seconds. It will reset the valve.
- Simulate the emergency brake situation and check whether your rear tyres are still locking up.
You can also adjust the Brake Proportioning Valve to control the pressure the piston needs to be closed. The higher the sprint preload is, the more fluid will be required to move the piston and close the valve. It increases the amount of flow to the rear brakes.
Take the following steps to adjust the spring preload:
- Locate the adjustment knob on the valve.
- Use the required screwdriver and undo the screws, holding the knob in its place.
- Rotate the adjustment knob counterclockwise until you hear a clicking sound.
- If you can’t hear the click, rotate it clockwise until there is a clicking sound. This will make the spring hold the piston tighter.
- After the clicking sound, tighten it all the way.
- Put the adjustment knob’s screws back in their places and tighten them.
Check out this detailed Video Guide on how to adjust your Brake Proportioning valve.
How to Test the Brake Proportioning Valve?
The only way to test a proportioning valve is by checking the pressure applied to the front and rear brakes. You must install a pressure gauge on each brake’s hydraulic circuits.
Turn on the engine and apply heavy brakes to mimic the real-time emergency braking situation; the pressure gauge will read the amount of pressure.
1. How to reset the brake proportioning valve?
Locate the valve on the rear brake line and press the reset button for a few seconds. It will reset the valve. Install a pressure gauge in brake hydraulics to test the result.
2. Can I repair my brake proportioning valve?
You can’t repair the valve. Don’t try to dismantle it unless you are trying to change it.
3. Can my car run without a brake proportioning valve?
The answer is no. Brake proportioning valve is essential for the braking system; without it, your car will keep locking up.
4. How can I know if my brake proportioning valve needs to be replaced?
If your vehicle’s rear wheels are sliding more than usual, it’s a good sign that your proportioning valve is faulty.