So the other day for no apparent reason my brake pedal got really soft than within two or three stops it went to the floor and the ABS and E-brake lights came on. Parked the truck and looked all over for leaks, nothing.
Checked the fluid, good.
Now when the truck is off I have pedal, start the truck in park I have pedal, as soon as I put it in drive it starts to get soft. when I drive, if I jump on the brake my pedal is hard as a rock but I'm pretty sure its just the fronts, If I apply the brake gently or let off pressure after jumping on it the pedal goes to the floor.
*ABS and E-brake lights are solid , rears are supposedly ABS however I have my doubts they ever functioned properly.
Its worth mentioning one of my cylinders in the rear are sweating a bit but the pads are dry. When I disconnect the fuse in the cab its worse. I have an ABS pump fuse under the hood even though I don't think I have an ABS pump, no power there. speedo works. E-brake also.
This is my only salt truck for this winter and I could really use some constructive input here, I'm totally lost for ideas at this point. I'd like to check the plug going to the solenoids so if anyone would have a diagram for that I would really appreciate it.

Thanks.

 

If the brakes work if you hit the pedal quickly, but not so much if you use them normally, you probably have a bad master cylinder.

 

you definitely have rear abs, it was standard on the trucks in this generation, however i dont think its related to your problem.

I agree with that_guy, sounds like a master cylinder, fluid is leaking out of the pressure side of the brakes, but you have plenty of fluid in the reservoir and no external leaks. Process of elimination says it must be leaking across the master cylinder.

 

thanks for the reply, sorry for the delay.
took it out in some light snow this evening and after 17 years owning this truck I think I can honestly say this is the first time I heard, felt the rear wheels vibrate..lol lack of a better word.
If its the master how is it that I have pressure when the truck is in park or when I jump on the brakes.
I've been watching the fluid , hasn't moved.
I was reading a post here about how to de-activate the piston in the abs module. but if I have ABS my thinking is its not the solenoid, but than again if the dump solenoid is stuck and only pops in with a quick jolt of fluid ?? any thoughts? I could really use some pro advice before attempting the abs piston jam, even though it was posted on this site

 

sorry, I forgot to mention I had stiff brakes in park whether the truck was running or not. and when I jump on the brakes they don't kick in than go soft, they stay rock hard till I lift off any little bit.

 

with the engine off you will always have stiff brakes because you have no power assist for the brakes.

however having good brakes in park is odd, but having them when you jump on them could make sense. The quick movement of the pedal builds pressure rapidly which pushes on the seals, this causes them to shift (usually a slight expansion) and build/hold pressure as long as that pressure is there, as soon as they are allowed to begin returning to their normal position the fluid begins to leak past them.