Symptoms of a Bad or Failing Proportioning/Combination Valve

The proportioning valve, also called the combination valve, is located in the disc braking system. It is responsible for controlling the braking pressure between the front and rear brakes. Equal brake force cannot be applied to all of the wheels on the car at the same time because the rear wheels will lock up. Vehicles with drum brakes in the rear have much lower pressure for the drum brakes than the front disc brakes. This is why the proportioning valve only lets a particular amount of pressure through to the rear brakes. If you suspect there is an issue with your proportioning valve, check for the following symptom:

Rear wheels lock up

Since the proportioning valve decreases the pressure sent to the rear brakes, the main symptom the valve is going bad is the rear wheels locking up when the brakes are applied. Furthermore, the wheels will lock up more easily on wet surfaces. The rear brakes may feel touchy when applied even gently. As soon as you notice the rear wheels locking up, contact a professional mechanic to have your proportioning/combination valve replaced.

How to check the problem

If you suspect you have a problem with the proportioning valve and want to test it on your own, there is a way to safely do this. Find an empty parking lot and have someone come with you so they can watch the back brakes. With the person safely away from the vehicle, drive the car and make a few medium to hard stops. Make sure to press the brake several times to simulate an emergency stop. If the rear wheels lock up and the front wheels turn normally, there is an issue with the proportioning valve. This test should be performed with extreme caution.

Best left to the professionals

Repairing and replacing the proportioning/conditioning valve is best left to the professionals because you are dealing with the braking system. While you can test the problem on your own, it is a good idea to have a professional mechanic fix the problem. Specialized tools are used by technicians to accurately diagnose failures that may not otherwise be noticed. The brakes are an essential part of your vehicle, and if you need to use them in an emergency, it is important they work correctly.

As soon as you notice your rear wheels are locking up, especially on wet surfaces, have your brake system checked by a qualified mechanic. The proportioning/conditioning valve is an important part of the braking system, so as soon as you see the symptom above, use caution if you have to drive the vehicle. YourMechanic makes getting repairs to your proportioning / combination valve easy by coming to your home or office to diagnose or fix issues. You can book a service online 24/7. YourMechanic’s qualified technicians are also available for any questions that may arise.


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Johnny

33 years of experience
264 reviews
Johnny
33 years of experience
Toyota RAV4 L4-2.4L - Brake System Inspection - Sacramento, California
Johnny arrived early which was great, he performed the inspection in less than half an hour, and gave us a complete quote for all items needing attention, including the brakes as our main concern. Johnny is fast and efficient so I scheduled the work done by him.
Ford Escape - Brake System Inspection - Sacramento, California
The convenience is worth the cost. I was also tired of the dealership not really caring about my old car. Last couple of times I had to wait well over an hour to get my car after the dealership said "It's ready!". They also wouldn't fix the things I asked saying they didn't have time and I need to come back.

Jay

37 years of experience
947 reviews
Jay
37 years of experience
Chevrolet C10 Pickup V8-5.4L - Brake System Inspection - Moreno Valley, California
Knowledgeable, Professional, Friendly, and PATIENT! Sickeningly HONEST, as I tried to ply him with cash, alcohol, outside work, and wild dancing girls - although I wouldn't have "ratted him out" if he HAD accepted. A guy like this needs a "bigger cut" than what you are paying him ... because loyalty like his is hard to find these days! THANKS!
Volkswagen Jetta - Brake System Inspection - Moreno Valley, California
As usual, Mr. Jay provides efficient and professional quality of work. I would highly recommend him to any customer searching for a good mechanic.

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10 years of experience
114 reviews
Christopher
10 years of experience
Ford Explorer V6-3.5L - Brake System Inspection - Katy, Texas
Christopher was very knowledgeable and was able to address our concerns. We would trust him with future service needs.

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16 years of experience
61 reviews
Jesse
16 years of experience
Nissan Frontier V6-3.3L - Brake System Inspection - Flagler Beach, Florida
Jesse took the time to explain everything that was going to be done and why and then proceeded to repair my truck not only professionally but quickly. As a disabled Veteran and no longer able to perform work that was needed to be done it is nice to know a mechanic such as Jesse will take the time to explain all the various issues and what needs to be done before a blanket you need everything. After Jesse went thru everything I felt comfortable that all work was required and needed. 8 can safely say I will use yourmechanoc .com again and hope I can request Jess

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