I have an 02 dodge 3/4 4x4 diesel. I have been having some issues with my rear brakes locking up as well the front. Every time i press the brake they seem to get tighter and tighter. to release them I just let off the line from the master cylinder let it bleed off and they become free. there is a little pin right there by the master cylender on an aluminum block seems to be a proportioning valve when my brakes are locked that pin is in the upper position and as i release the pressure it goes to the lower position. in looking for the problem I have replaced both back brakes (cylinders) and one front (of which had one of the pistons broke and when i pryed it out of place it fell out of the housing in about 10 pieces ). As well one of my rear brake shoes had fallen from its guide and wedged itself between the guide and rotor and had been bent severely due to the pistons prying at it. and after replacing all of these parts and discovering all these small issues as well my pickup still has a problem not releasing pressure after the breaks have been applied. any ideas would be greatly appreciated. any pressure tests or mechanical tests I should know about would be great.

 

This sounds like a master cylinder issue, since the pressure releases when you open a line at the master cyl. We had some problems with one of my grandfathers trucks not releasing several years ago. Turned out it was the flex brake line. The inside of the line had let go, and was acting kind of like a check valve.

Jeff.

 

Just a quick question flex line meaning from hard line to brake cylinder?

 

No, on his truck it was a flex line down by the wheel.

jeff

 

ok just a hose from the solid steel line to the brake calipers on the rotors that is easy enough to check. just digging straws trying to get somewhere on this thought I had it when I found the busted caliper.

 

I agree It sounds like a master cylinder prob. There could be crap in the brake fluid clogging the line and acting as a check valve also. Id replace the fluid and check for crap in there. And if thats not it. Replace the master. Sorry cant be more help