1992 F250 4x4. Can a bad RABS valve cause a soft and low pedal? The truck will stop but the pedal keeps going down. I have done a Search and found other probable causes. However, I need to know if it is at all possible that a bad RABS valve can cause the above symptom.

thanks and Happy Trucking

 

It is possible, but they way your describing the pedal makes me suspect a master cylinder bypassing internally. One way to test that is to leave the engine off and pump up the brake pedal till it's firm and then keep your foot on it and see if it's still going down.

 

Thanks for the reply.

We just replaced the master cylinder - twice - (once from NAPA, now from FoMoCo). Which is why the valve is now suspect.

 

A defective solenoid in the RABS valve body can cause a sinking pedal. The valve body is on the inside of the left side frame rail around where the drivers feet would be. If you want you can remove the large hex plug on the end of the valve (under spring pressure all the way off). Remove the spring and replace the hex plug. Pump the pedal a few times to fill the chamber with fluid. If the pedal no longer sinks you know the RABS valve boby is faulty. If it still sinks put the spring back in and look elsewhere. You can still drive the truck without the spring you just will not have ABS. Good luck.

 

OK. Thanks for the a much appreciated and extremely helpful replies!

 

The best thing you can do is bypass the RABS valve with a piece of brake line. The RABS never worked that well to begin with.