Brake Issue

Bronczilla · May 12, 2008

When I press on the brake pedal it stays compressed and does not release. Kinda like an e-brake.

Within the last month I have:
Replaced the brake valve on the frame and brake lines.
New shoes on the rear
New Wheel cylinders
New Master cylinder and Booster
Flushed the system and replaced w/ fresh brake fluid
Vacuum to the booster checks good

Thinking about isolating the front and rear to see which is sticking, any other ideas.............getting fusterated and need fresh eyes.:eeek:

TigTorch · May 12, 2008

So obviously with any troubleshooting comes a couple of questions. What happened just before it started doing this; underwater, rollover, panic stop, extended storage? And what is the history of your rig. Any used parts that were left out in the weather with no caps on the lines, junkyard master cylinder, rubber parts 20+ years old?

As far as throwing out ideas here goes mine:
Brake linkage binding in cab=unlikely
Brake line on axle smashed flat from rock=maybe
Proportioning valve crudded up/stuck=maybe
Something funny with vacuum booster (not rigged properly/assembled incorrectly/wrong part number/bad used part)=probably

I'd start cracking open lines and see of its hydraulically locked and if /where it frees up.

Bronczilla · May 13, 2008

It dosent get wheeled that much, its stored inside an unheated shop. Not sure what I did last, it was rolled, hit hard in the front and some hard stops. The linkage is not binding, all brake lines are undamaged. I will try your other suggestions. Thanks.

Fordzuki · May 13, 2008

Sounds like possibly the rubber lines are collapsing, allowing the hydraulic force of the fluid through, but not allowing it to return.

Bronczilla · May 13, 2008

Fordzuki said:
Sounds like possibly the rubber lines are collapsing, allowing the hydraulic force of the fluid through, but not allowing it to return.

I replaces the rubber lines w/ steel braided lines.

64FJ40 · May 13, 2008

How much freeplay is there on the pushrod into the booster at rest? how about from the booster into the m/c?

It seems like most of the time these problems come up it's because the master isn't fully releasing. Pump up the brakes to where they're locked up, then back off the nuts holding the master cylinder to the booster a couple turns each and see if that releases the pressure.

BustedPinion · May 13, 2008

I Dont Know About Your Type But In My Career I Have Came Across This 2x, Both Times It Was The Booster Broken Internally :; AND THEY STILL HELD PRESSURE..