Well last monday I wrecked my truck (96 2 wheel drive)due to the breaks going out. I found that the line from the p valve to the front breaks was blown. I pinched the line after the valve and and easied the truck home. I changed the line and the breaks still wouldnt hold any pressure. I thought the line that goes from side to side may have a pin hole under the rubber coating so I changed it. I still had the same results so I changed the master cylender and blead the breaks again. Still same results. As long as I plug off the front breaks it will hold pressure and wont blead off. Anybody have any ideas what is going on with my truck? Is it possible that the P valve is messed up? thanks in advance Eric

 

Its got air in it somewhere is what it sounds like if you pinch the line off. They can be a b!@ch to bleed some times does the peadal "pump up" if you can pump the peadal up and get it to hold and then have a buddy just crack the bleeder then close it and repeat. If it wont pump up just slowly pump the peadal a few times and hold it down and do the same have a buddy crack the bleeder and close it. And with bleeding brakes you always want to start with the bleeder furthest from the master in this case would be the pass side bleed this one until you dont get any air and then move to the drivers side. And one thing to remember when bleeding brakes is to pump the pedal slowly down slow and up slow as to not flip the cups in the master cyl some times rare that this happens but it can if you mash on the pedal quickly with air in the system. And too make sure you keep an eye on the fluid level in the master when the air starts to escape it will pull the fluid level down pretty quickly. Try bleeding them like this and see what happens.

 

sounds like u arestill getting air from some where check your calipers and line to them

 

I have blead over 2 bottle of break fluid thru it and I did it just the way that blkjack described. The peddle will pump up a little pressure but before I can even crack the bleeder it goes to the floor and hardly no fluid will come out. I agree that it is acting as if it has air in it still but shouldnt all of the air be gone after bleeding it that much?

 

Does the truck have RABS? If so you might need to push the reset button on the side of the RABS unit....there should be a black button on it. Do you have a FSM or Haynes Manual?

 

yes truck has rabs, I dont have a manual. Where is the unit located at?

 

On my '98 the block is up under the hood by the M/C. I think it's the pressure relief valve. It will trip if it senses a pressure difference and closes off the front or the rear brakes where the pressure loss is so that way you have some brake pedal if I understand it correctly. It should look like a prop valve with a blach button on the side. I think you have to push it in to reset it

 

I will check into that right now and get back with ya, thanks

 

I don't know if that is it or not but it's easy to check. Also I found it's easier to bleed the rear brakes if you tie the load sensing prop valve up so it lets full flow through to the rear wheel cylinders.

 

the rear break system hasnt ever been broke or ran out of fluid, So I shouldnt have to bleed it at this time. thanks for the tip tho.