Exception in rendering!

Message: window is not defined

ReferenceError: window is not defined
    at new c (/tmp/execjs20161209-102960-mjbio4js:136:3912)
    at m.mountComponent (/tmp/execjs20161209-102960-mjbio4js:47:15602)
    at /tmp/execjs20161209-102960-mjbio4js:49:31860
    at a.r.perform (/tmp/execjs20161209-102960-mjbio4js:47:12503)
    at Object.a [as renderToString] (/tmp/execjs20161209-102960-mjbio4js:49:31821)
    at r (/tmp/execjs20161209-102960-mjbio4js:50:21164)
    at Object.S.ReactOnRails.serverRenderReactComponent (/tmp/execjs20161209-102960-mjbio4js:32:6073)
    at eval (eval at <anonymous> (/tmp/execjs20161209-102960-mjbio4js:173:8), <anonymous>:10:23)
    at eval (eval at <anonymous> (/tmp/execjs20161209-102960-mjbio4js:173:8), <anonymous>:17:3)
    at /tmp/execjs20161209-102960-mjbio4js:173:8

Symptoms of a Bad or Failing Proportioning/Combination Valve

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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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

Post a question and get free advice from our certified mechanics.

ASK A QUESTION

More related articles

How to Get a Louisiana Driver's Permit
s licensing program. The first step in this program is to obtain...
Veteran and Military Driver Laws and Benefits in Idaho
The state of Idaho offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch in the...
Veteran and Military Driver Laws and Benefits in New Mexico
The state of New Mexico offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch...


Related questions

Q: The securilock won't let me start the car

Hello, thanks for writing in. Typically when the gauges move like this it is due to a voltage issue. Most of the time it is because the battery has failed. In some cases it can just be the connection at...

Q: My engine is knocking

When your car begins to knock due to a lack of oil, this could mean many different things, such as broken or bent valves, a bad camshaft, rod or main bearings, and many other different things. As you may know,...

Q: Car vibrating after I heard a loud noise while using the brakes in reverse.

It sounds like something may have broken internally within the transmission. I would recommend having your vehicle inspected by a transmission expert to get to the bottom of the issue. If brake applications still feel normal, but the vehicle vibrates...