Really need some help here, I'm hoping someone has had a similar issue and can give me a bit of guidance, because I am stumped! 2004 Dakota SLT Extended Cab, 4WD, 4.7, Automatic, Rear ABS. I bought the truck a few months ago, previous owner installed new master cylinder, brake booster, and rear calipers from what I can tell. I drove it back (4 hours) without any incidences, but when I put it up on a lift, I noticed the front brakes were not releasing all the way, they were dragging. Figured everything else had been replaced, I replaced the front calipers, bled the brakes all the way around, and all seemed fine. 3 months later and it started dragging again, and over the course of a couple weeks, it stranded me on the side of the road by locking the front brakes. It'll feel like a good, normal pedal, then I'll go to brake, and the pedal will be SOLID! I get barely any pedal movement, sometimes it gets better, other times it'll tighten up and I'll end up pulling over because the truck can't push it. I bled the brakes (on the side of the road) and get some more air out of the front and got home and back to work the next day, but they were getting tight again by the time i got to the shop. It is so seemingly random and we're just lost as to a cause! Any clues guys? My thought is that the master cylinder is the problem since that's the only single item controlling both calipers. It's not the booster, we tested that already. Please help me out if you have any ideas. I don't want to sell this truck.

 

Welcome to the forum!

Are you getting a brake warning light?

A couple of things, it is possible for the flexible brake lines to break down internally and act as a check valve so the calipers can't release.

A bad master cylinder can certainly cause your problems. The air in the system, after bleeding, is not normal.

Don't rule out the power booster so quickly. There is a valve in it that allows for an equal vacuum on both sides of the diaphragm when the brakes are released. When you apply the brakes, it allows normal air pressure to enter the rear chamber and this helps apply the brakes.

Depending upon what the valve is doing this can cause your brakes to drag and it can also cause the pedal to be solid - no assist.

 

There is no Brake light on, until I disconnected the ABS fuse(which is back in). We eliminated the booster by pulling the master cylinder off of the booster and the brakes were still tight. I can't believe that broken down hoses can put enough pressure at the calipers to smoke the rear tires trying to move the truck! I'm thinking the air in the line when we bled them was caused by brake fluid boiling.

 

Replace the master cylinder.

 

and replace the brake lines. Had one collapse on our dually once, locked the right front up soldi at 45 MPH with a trailer attached.

 

The flex brake lines are cheap and easy to replace so why not replace I always say.


Have you flushed out all the DOT 3 yet it may be contaminated that's cheap to do also.


If the DOT 3 was contaminated it may take more than one flush.


In fact some of your problems sound like the DOT 3 is contaminated.