Jeep help

[jchrisk1]

Anyone ever mess with jeep brakes? I am having a hell of a time with mine. I have bled these brakes 5 times now with no luck. It's an 81 cj7 with power brakes.
I've adjusted the shoes on the rear, new master cylinder (bench bled), I depress the proportioning valve when bleeding, and the calipers are on the correct side with bleeders on top of the piston.
They will be hard when I finish bleeding them, but when I start the motor they are soft again until the shoes make contact then it is hard to stop. I am thinking I'm not getting any front brakes. Maybe the Proportioning valve is bad. I don't know and am at a loss. The only way that I know of to check the PV is to replace it.
If anyone has any experience with jeep brakes, please help.

Thanks,
Chris.

 

[ReycleBill]

Maybe I'm wrong but I always bleed power brakes with the engine running.

Recently we had a strange problem on my brother's Dodge caused by a new rubber brake line that swelled up like a small balloon when the brakes were applied. We bled and bled for weeks and never could get pedal. Everything was new-- everything. Then by chance we found the bubble in the new line. Just looked down and said, "Hey, that's strange!" Took the line back for another and had her going in no time. Stopping too.

 

[jchrisk1]

I forgot about the rubber lines. I was going to check those next time I messed with it but that was a month ago and I forgot. They are old and I thought they might be swelling.
As far as the engine running while bleeding, I don't find it necessary as it doesn't take much pressure to bleed the lines. If anything, in my opinion (which may be wrong), Is that the pressure from the booster breaks the air bubble into thousands of tiny bubbles making it harder to get out. Same with pumping them.

 

[ReycleBill]

I forgot about the rubber lines. I was going to check those next time I messed with it but that was a month ago and I forgot. They are old and I thought they might be swelling.
As far as the engine running while bleeding, I don't find it necessary as it doesn't take much pressure to bleed the lines. If anything, in my opinion (which may be wrong), Is that the pressure from the booster breaks the air bubble into thousands of tiny bubbles making it harder to get out. Same with pumping them.

You might be on to something with the pumping causing bubbles. I was taught to always pump very slowly to reduce bubbles.

How old is your jeep? Does it have antilock brakes? If yes then I'm in way over my head.

 

[jchrisk1]

It's an 81. No ABS. I have never had so much trouble with brakes as I have with this jeep.
I've narrowed it down to booster, proportioning valve, or brake lines. Well, at least those are the things I haven't replaced yet. I don't have any leaks anywhere. I'll get my kid to push the pedal tonight so I can check the front rubber lines.
It's driving me mad. If I don't get them fixed soon, well it's cold on a bike in winter. Not that a jeep is much warmer. But at least the windchill is gone.

 

[ReycleBill]

It's an 81. No ABS. I have never had so much trouble with brakes as I have with this jeep.
I've narrowed it down to booster, proportioning valve, or brake lines. Well, at least those are the things I haven't replaced yet. I don't have any leaks anywhere. I'll get my kid to push the pedal tonight so I can check the front rubber lines.
It's driving me mad. If I don't get them fixed soon, well it's cold on a bike in winter. Not that a jeep is much warmer. But at least the windchill is gone.

One word: Fairing.

 

[ReycleBill]

One word: Fairing.

PS. Are you sure the kid is holding the pedal down while you tighten the bleeder fitting? I once crawled around under a car for hours because my little brother kept taking his foot off the brake too soon.

PPS. Have you tried bleeding into a bottle of brake fluid?

 

[jchrisk1]

I had my wife helping me bleed them and I always bleed into a bottle of fluid. It only took a few times of me telling her "quit letting off until I tell you" before we were on our way.

I just started it up and had my kid step on the pedal a few times to check the rubber lines and they are fine. One side is anyway, the other side didn't look like it was getting any pressure which makes me think it's the valve. So, I guess I will be buying a proportioning valve and hope that's it. It seems to me the booster is working fine.

I've had older trucks with front disc and rear drums that didn't have a PV and I never had any problems with them stopping. I don't really know why it is even there. Maybe because the jeep is so light. Never having dealt with one before makes it hard to be sure that is the problem. I can feel my pockets getting lighter every time I work on this thing.

 

[ReycleBill]

Use of the PV depends on the size of the brakes and weight of the truck. Older trucks had smaller drums on the rear. Replace the PV but don't delete it.

The only thing I can tell you for certain is that it's something simple. But then aren't most things? Good luck and please tell me what it is.

 

[jchrisk1]

Well, after much forum searching and googling, I found that on these proportioning valves you have to bleed the fronts first to center the valve. Then go to the backs and then the fronts again. I will be trying this today and I hope this does the trick. If not, they say I have to take the PV apart and clean it as the valve is stuck from corrosion. Which, after seeing the old fluid, is probably the case. Because nothing has been easy with this jeep.