Skip the auto shop - Our mechanics make house calls

Symptoms of a Bad or Failing Proportioning/Combination Valve

proportioning combination valve

Bad or Failing Proportioning/Combination Valve Inspection

by a top-rated mechanic at your home or office

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:

HAVE SYMPTOMS OF CAR TROUBLE?
Get an $80 diagnostic
by a top-rated mechanic at your home or office.

Get a quote · Book an Appointment · Our expert mechanics come to you.

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.

HAVE SYMPTOMS OF CAR TROUBLE?
Get your car fixed at your home or office.

Get a quote · Book an Appointment · Our expert mechanics come to you.

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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Still not sure about your car's issue?
Diagnose your car
What kind of issue are you experiencing?
Brakes are squeaking
Car is not starting
Car is overheating
Car is shaking (vibrating)
Fluids are leaking
Heating and A/C
Smoke or steam is coming out of the car
Warning light is on
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

Symptoms of a Bad or Failing Flexible Clutch Hose
Common signs include difficulty shifting, low clutch fluid, and feeling no resistance at the clutch pedal.
P0121 OBD-II Trouble Code: TPS "A" Circuit Range Performance Problem
P0121 code definition Throttle Pedal Position Sensor/Switch (TPS) A Circuit Range Performance Problem What the P0121 code means P0121 is a generic OBD-II code which indicates that the Engine Control...
Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...


Related questions

Q: How do I release the steering wheel lock?

Your car features a steering lock system that prevents the steering wheel from being turned under certain conditions. For instance, if the ignition is off and the electronic key is not nearby, the wheel cannot be turned. This is a...

Q: Stalling problem

Hi there, thanks for writing in. Your car has an idle air control valve that commonly fails. The purpose of the idle air control valve is to allow enough air to bypass the throttle body to keep the car idling...

Q: Put new brakes on, car feels like its in park when in drive/reverse

Hello. I will try to assist you with your 1999 Jeep. Remove the two wheels you worked on. Apply and release the service brakes several times and return to the wheel positions (with transmission in neutral, block rear wheels and...