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My rear brakes were occasionally locking up on me when I come to a stop. My OEM Ford Manual listed the proportional valve as possible cause. I have no Brake or ABS Warning Lights on although they self-check OK during start. I replaced the proportional valve which I purchased from the Gaudin Ford on-line parts sale. It didn't solve my problem but further troubleshooting I was able to determine and correct the problem. Can anyone tell me how the proportional valve works? It seems like it allows bake pressure to go to the RABS valve but as the pressure increases to a certain level, it forces a valve inside to limit the pressure.
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