I was driving the truck and everything has been fine and then I go to step on the brakes and the pedal went all the way to the floor, only the front brakes were stopping the truck. After jacking the truck up I found the rear wheels would not even slow down when I tested the brakes with the rear wheels off the ground and the truck idling in drive. There are NO leaks and I ended up bleeding all four wheels just because I didn't know what else to do but still no rear brakes. I did put a new rear brake line that runs from the front to the back along the frame and along side the fuel tank (rusted out) However that was about four weeks ago or about 60mi ago and everything has been fine until now. I have NO warning lights coming on. Any help PLEASE.

 

there is usually an isolation valve to seperate front and rear if one system fails like a check valve it keeps you from blowing all fluid and losing the other good set of brakes if a leak occurs it must be reset its like a lil tit that sticks out of the side of a housing someplace anyone else have anything to add on this did one on my 81 cutlass when my rear brake line failed only had front brakes till i fixed line and reset and rebled the system

 

Thanks Scott

That's kinda what I thought it might be but I can't find anything that I reset, Hopefully somebody can tell me where to look.

 

I removed the master cylinder to see if it needed to be bench bled, but it was already bled and worked fine. I am still lost, what else could it be??

What is this aluminum block with the five brake lines going into it?? could there be a problem in that?? Please help!!!!

 

Thats your ABS pump I believe

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Yea after going back and lookin at the pic it's the ABS pump, and probably your problem, but check your fuses and there's probably a sensor on the rearend somewhere you can check also. The pumps are big bucks if thats the problem, and some people just bypass them you'd just lose the ABS that way

 

Thanks Tiremann......How would go about testing that thing and how would go about by-passing it

Thanks

 

The problem has been fixed.........What it turned out to be was the master cylinder. When I tested mine I "thought" it had enough resistance when bench bleeding it, however, after talking with other people what I found out is, you should NOT be able to push the plunger in (except for about 1/8 to a 1/4") on a master cylinder IF it is good and has been bled correctly. On my master, I could push the plunger all the way in till it bottom out, it was hard to do but I could do it and it never got any harder wile I kept trying to bleed it. On the new master after I started pumping or (bench bleeding) it was starting to get harder & harder after about 5 minutes of pumping till I could no longer push the plunger in more than about 3/16 of an inch.