Im really stuck here. I posted earlier about not being able to bleed my brakes still with no resolution. Truck is a 96 dakota v6 4x4 rear abs. The ABS light is on FYI.

When the truck is off, they feel good. Even driving they stop the truck ok, but could be better. THe pedal will almost go to the floor with the truck on, off its rock hard. This is the 3rd master cyl and this time it is a new one, not reman. New calipers, lines, blew out the lines, no clogs, bench bled the master cyl, cricked the lines loose out of the master cyl think air might be there. THen we did 20 cycles of pedal bleeding on each wheel, fluid is clear and no more bubbles. Then vacuum bleed each wheel with a HF vacuum bleeder. I put teflon tape on the bleeder screws before this so air wouldn't go past the threads and I could see any air that came out. A few bubbles came out of the two rears and the pedal felt slightly better. The ABS light is now intermittent, so I know there is still some air in the system somewhere.
I feel like ive tried every trick in the book. Tapped on the master cyl, calipers, wheel cyls. There's no leaks anywhere. Its been a month since ive had good brakes. I've taken the master cyl off about 7 times now, to bench bleed it again, and still the brakes never get to feeling good. Turned the truck on and bled them, no better. Just clear fluid.
Does anyone have any ideas. I don't know where to go from here.

 

Have you someone pressing the peddle while bleeding?For all that you've done there shouldn't be any problem HUMMM...

 

Your proportioning valve has shifted and stuck to one side more than likely. When there is air in the system or someone does a brake job and stomps the pedal instead of slowly pumping up the brakes, even really low brakes and having to stand on them to stop will cause this to happen. I've done it accidentally before......forgot that I didn't pump them up and took off out of the stall...lol.

The valve being shifted like that will cause an ABS code...I think the name of the code is "Foundation Brake" or something like that.

 

Thanks for the advice. How do I reset the proportioning valve or clean it or whatever to get it back to normal? Thanks again.

 

Probably have to get a new one. I have been able only once to get one to shift back into position by tapping it with a hammer while someone slowly pumps the brake pedal. It's tricky.

Quote:

COMBINATION VALVE

 

You mentioned that your ABS light was on, do you have the ABS module installed in your truck? If you do, there is a different procedure to bleeding vehicles with ABS than bleeding without ABS.

 

I do have an ABS module. My truck has only rear abs. I read through the service manual and saw nothing the mentioned a special procedure, but if you know of one please do tell me, Im willing to try anything. Someone told me that vacuum bleeding would bypass any special ABS bleeding procedure, so i tried that but had no luck. If I do need to get a new one, does anybody know where I can purchase one?

 

ANother thing, if I do the tapping it with a hammer method, how would I know if it went back into position?