Brake Problems...

I'm running a remanufactured MC. It has worked fine for months, and I know that other early CJ owners are using it. It's set up for drum/drum.

A few weeks ago, I noticed that the driver's front wheel cylinder was not releasing. The brake lights would stay on, even when you took your foot off the brake pedal. When I got home, I'd have to open the bleeder screw and release the pressure.

I assumed the wheel cylinder was gummed up and wouldn't release, so I ordered up both front wheel cylinders and new pads. I installed everthing and it worked great... for about a week.

Last night I drove the Jeep a little and noticed that when I put her back in the garage, the brake lights stayed on. Sure enough, when I opened the bleeder screw on the drivers side front, fluid came pouring out.

What could be casuing this? All the springs holding the pads on had plenty of tension, so those aren't the problem. As I said, the wheel cylinders are brand new. The MC is set up for drums, so the proportioning valves should be 10 pounders. Is it possible that I could have the brakes adjusted out too far? There is next to no play in the pedal. Pretty much as soon as you step on them, you're stopping.

Any thoughts?

 

Are these manual or power brakes? is it a dual or single reservior master cylinder? there is rod which pushes on the master cylinder when you apply pressure to the brake pedal. The rod should have an adjustable length. If it is adjusted too far out, it will apply pressure on the master cylinder even if your foot is off the brake pedal. I would check this rod and back it off 3 turns, see what happens, and go from there.....

 

Billy - All lines are stock (well, I replaced a few, but I bent them just like the stockers, and the follow the stock routing). What are these "pressure loops" that you speak of?

Linckeil - Good point here. I had to modify the push rod slightly, and it doesn't have adjustment. But, they have worked fine for several months. I'm not sure why this would become a problem now...

Edit - Manual brakes, dual chamber MC

 

Hmm. I always thought they were there to allow flexing between the body and frame (b/c most MC are mounted to the firewall and the lines run to a rigid mount on the frame).

Learn something new every day, huh?!!!

 

Since the system is free of air (at least I think it is free of air ...the bleeding of the brakes) I would think the lines (and the whole system) is 100% full of brake fluid. It is a sealed system of brake fluid that is compressed by the master cylinder to actuate the wheel cylinders.

I am not an expert but I don't think air is in the line.

 

Thanks Dan!

Unfortunately, it's not just the switch. I can tell that the driver's front isn't releasing b/c I don't have to hold the brakes at a stop light to keep from rolling!

 

I didn't modify anything, but I did change out most of the parts - including the rubber lines. They were not used, but had been sitting on a shelf for a while, and it's possible that they are clogged with something. I'll have to take that one off and see if it's blocked.

Good idea Glenn. Thanks!!!

 

I had lots of problems with a VW Beetle's brakes once and the culprit ended up being the rubber brake lines. They were clogged-up. Could be one of your rubber brake lines is allowing flow in one direction but pluggining up on the opposite direction (pressure release).

 

I've know of the rubber lines seperating on the inside and then a flap of the seperated part will act lilke a valve and not allow the fluid to flow back into the master when the pedal is released. That would explain the wheel being hung, but it would not explain the lights staying on. If you have drums all the way around there is not a prop valve in the system only the residual pressure valves in the M/C that help keep a very small pressure in the lines 10lbs IIRC. Isn't the switch screwed to the bottom of the master? The one I took out of mine when I upgraded to discs this spring was there. Might be 2 problems you are chasing. Just a thought.

 

what about the residual check valve in the master cylinder? maybe its sticking and not allowing fluid to return?

 

I *have* a pressure switch up front and in the back, but only the back is hooked up. Good point Brian (Hurt) - I didn't think of that...

I will swap out the brake hose with another that I have and see if that corrects the sticking cylinder. If the lights continue to stay on - I'll then tackle that problem. I think you might be right Brian (Smith) that there are two different problems here...

 

Negative - Dual chamber MC with seperate ports for front and rear.