2nd Gen Non-Engine/Transmission Brakes Broken

[DMcQuown]

Help PLEEEASE!!

I have a 1996 CTD 2500. I have been battling a brake problem for a few weeks now and finally ready to give up. Problem... while holding pressure on the brake pedal, the pedal slowly goes to the floor. I checked the calipers and rear brake cylinders for leaks, found a few bad brake lines and replaced them while I was in the mood. Blead the brakes, no air in the system and the problem persisted. Next was the master cylinder... figuring this had to be the problem. . brand new master cylinder, blead the brakes, no air in system. . hit the brakes, nice hard pedal then while holding---to the floor it went.

I looked, checked and rooted in out and around everything. Master Cylinder stays full of fluid, No visible leaks, and no air in the system. NOW WHAT should I do. Anyone who might have experience this problem or anyone who can give me information to fix this painful problem... . I would greatly appreciate it.

Sorry so long and thank you in advance,

Dan

 

[RDelissen]

something similar happened to mine last night while replacing the right front caliper (the old one was dragging, but still worked).

Bled the system and it'll hold the brakes with engine off, start the engine -> pedal goes down to the floor. And it ain't leaking or anything.



So my first action will be: get another caliper and see if that cures the problem ...

 

[DMcQuown]

Ok gentlemen, here it goes. After going yet another $74 in the hole in attempt to fix this problem, I purchased two calipers for my truck. Installed both, manually bled the brakes yet again to no satisfaction. I then installed two new brake hoses from the caliper to the steel lines. Bled the brakes again, this time trying the gravity blead method. Took a little longer but the same results.

I to have a hard pedal without the engine running, start the engine... . apply the brakes and hold. Slooooooooowly to the floor goes the pedal. Only three items left and I will have replaced every single component in the system. Brake booster and RWAL valve and differential valve. Any suggestions? Stay tuned for further updates but now I am leading towards the RWAL valve. One says it could be the Booster however I put a guage in line. 26 pounds of vaccum. Apply the brakes, loose 6 lbs and back up it goes. Hold the brake with the engine running and the vacuum stays there.

Ok guys lets take a pole to see which one cures the problem. A) RWAL valve, B) Differential valve or C) the Brake Booster.

 

[dslmacdown]

I vote for A) RWAL valve. Years ago I had a Chevy that had the same problem and I replaced the master cylinder about 4 times thinking I kept getting bad MC's. Until someone told about the anti-lock, turns out the dump valve in the RWAL was leaking causing spongy pedal. You might try driving and slamming the brakes hard enough to activate the ABS, this will cycle the dump valve and flush any dirt or crap stuck in the valve.

 

[Missouri Mule]

Did you bleed the master cylinder?

From 96 service manul "A brake pedal that falls away under steady foot pressure is generally the result of a system leak. "

 

[RDelissen]

what we figured out the other day on mine, is that the bleeder valve doesn't screw in completely so it's probably sucking in air ... it however does not leak brake fluid. We'll see what happens when the new caliper comes in

 

[BigIronRam]

You bought a NEW or rebuilt master cylinder? If it's rebuilt I'd take it back and go for the new one. One day I put three rebuilt starters in a row on a chevy, yep, all three were bad. I spent half my time chasing things that weren't bad just certain the starter COULDN'T be again...

 

[RDelissen]

what we figured out the other day on mine, is that the bleeder valve doesn't screw in completely so it's probably sucking in air ... it however does not leak brake fluid. We'll see what happens when the new caliper comes in

well it doesn't seem to be the caliper causing the problems, so on to a new master cylinder now to see if that cures the problem



Sorry for hi-jacking the thread, but it might help in future searches