02 WRX bad proportioning valve??
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This is a discussion on 02 WRX bad proportioning valve?? within the Suspension & Wheels forums, part of the Tech & Modifying & General Repairs category; Not sure if anyone else has experienced this or not, but any input would be greatly appreciated. Last fall rear ...

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    02 WRX bad proportioning valve??

    Not sure if anyone else has experienced this or not, but any input would be greatly appreciated. Last fall rear brakes would not release. I was able to limp it home with a surprising amount of smoke coming from the brakes and those critters were HOT. I replaced the calipers, rotors and pads hoping this would fix the issue...it didn't. Took it to a local garage who replaced the rear brake hoses and said the proportioning valve was failing. At the time Subaru did not have the valve in stock, apparently there was a shortage last year for this part. I believe Subaru calls it a "PCM or PCV" (pressure control valve or module)...can't remember. Anyways, having the brake hoses replaced did seem to work for a few weeks, but as luck woudl have it the brakes would not release again. So took it to a Subaru dealership and had them look at it. They replaced one of the rear calipers (not sure why), replaced pads and flushed the system. They did not replace the proportioning valve as they could not replicate the problem. So...I am still having the same issue...rear brakes will not fully release. Has anyone else had/have this issue? There are no modifications done to the car. Other than remanufactured calipers, the rotors are OE as are the pads. Absolutely no issues with front brakes. Is it the proportioning valve or is it the master cylinder?

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    Registered User Obeisance's Avatar
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    How did you confirm that the rear disc brakes were the problem? Is it possible that the parking brake cables caught on something under the car and are causing the issue?

    Also, I think that the PCV valve is for positive crankcase ventilation (to control engine pressure on the side of the piston opposite from combustion) rather than brake systems, right?

    Alternately, could this be a problem with the ABS system? I think there may have even been a recall ( Subaru Recalls: a list of recalls on various model- Outback, Impreza, Legacy, WRX, STI, Forester, Tribeca, Crosstrek, BRZ ) on the bugeyes about the ABS, but it wasn't related to the symptoms that you're describing.

    edit: I just did a search on google about the proportioning valve- I guess that it is not too expensive of a part. Since your rear brakes are sticking maybe you could try switching this part for a new one.
    Last edited by Obeisance; 03-04-2014 at 05:21 AM.
    David - '05 WRX

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    I think my confirmation was the calipers were...really hot and the pads were ground up something good. Also the smoke coming from the pads was a tell-tell sign. Checked the parking brakes, no issues with cables and backed the shoes off the second time it happened just to make sure it was not the parking brakes sticking.

    The part is PMV - pressure metering valve aka proportioning valve. I couldn't remember the name Subaru used, had to look it up.

    Subaru checked the ABS and found no issues and at no time has the ABS light come on, which I do understand means nothing as it is an "idiot" light.

  5. #4
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    It is very possible that the proportioning valve has failed. In typical operation, the brake proportioning valve diverts pressure away from the rear brakes to shift the brake bias forward under hard braking (in-line with the weight shift on the axles). I'm not familiar with the failure modes of the brake proportioning valve, but I suppose it could fail and lock up hydraulic pressure to the rear brakes permanently. Perhaps someone with a bit more knowledge of the system could chime in.
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