Brake pedal suddenly dropped very low

[Johann65]

[hitlers revenge]

Cool Bananas, glad you got it sorted.

Doug you have mail.

[KSF]

Hi Kavesh - to isolate the problem, same old story. Put a vice grip on each rubber brake pipe and nip it closed. If your master cylinder is okay your pedal will be rock hard, and right at the top. Whilst sitting behind the wheel with your foot on the pedal get someone to remove the vice grips, one at a time. Your problem wheel/s will show when the pedal drops.

Good luck,

Doug

Quick note to say thanks Doug (and AMC in general for the info one gets here).

I had been struggling with a long and soft pedal on the Sierra and after a master rebuild, then master replace and endless fiddling with the rear calipers (two weeks and about 8 bleeding sessions!), even replacing the biase valve with an aftermarket one, I still had not progressed one bit. Sitting in the car pumping the pedal and hoping for inspiration, this bit of advice above sprang to mind. And yes, about 5 min later I knew exactly where the problem was! Front calipers. Still not sure what their problem is/was, but replacing them with another set solved it.