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HELP, M/C keeps leaking!

egghead

egghead

NAXJA Forum User
NAXJA Member
Location
Parke County, Indiana
Around three weeks ago, I put my lift on the MJ. Got everything done, ready to drive besides the brakes.. Went to bleed the brakes and couldnt get pedal. Replaced the master cylinder with a rebuilt one, Master cylinder went bad, I repeated this 4 times. The last two were new ones. I do not know what is going on.

First I thought I wasnt getting brakes because of the porpotioning valve, so i put one on there from a 94 Cherokee. well, everything was fine, but the master cylinder leaked. I never could get brakes.. I could get a lil' pedal, but it would not hold.. If you held on it, it would go to the floor. What am I doing wrong?

When I did the lift, I also replaced the axles, the rear is an 8.8 with disk brakes. The front is a D30, both axles were dry. I also replaced the front rubber lines with wrangler lines. Replaced the rear hard lines, there is only one little section that runs across the engine compartment, and along the frame under the bed. Those are the only old lines on it.

Egg
 
Along the frame under the bed is a noted place for the hard line to rust and fail.
The part above the gas tank usually, mud and crap get's up there and rusts out the line. Check there for a leaky line.
Did you bench bleed the master cylinders? A dry master will just keep sucking it's own air bubble back in when you try to bleed them the conventional way. Either bench bleed it or vacuum bleed it. Vacuum bleeding is the easiest way.
 
Thank you for the impute...

Manche, I did change the line by the gas tank. I changed that when I first got the Jeep. The guy had blocked off the master cylinder because the hard line was leaking in the back.

Yes, I properly bench bled the master cylinders.

when I bled the Jeep (this is why I didnt understand why I wadnt' getting brakes) I used a couple methods..

Vacuum Bleed: I had a hand pump vaccuum bleeder and one that you hook up and air hose to a canister, and it sucks the fluid out..

Old Fashion: I did the old fashion, pump... break the bleeder open, etc.

Today, I used the flush type. The type that is a canister that has brake fluid in it. It pushed fluid through the master cylinder and to the bleeders. Break the bleeder open and let it run. After doing this, I regular bled it a couple times, and one of my buddys told me the M/C was leaking. Sure shootin' it was leaking between the M/C and the booster.

Thanks

Egg
 
did you get the master cylinder that has the plastic resorvoir or the metal one?
 
I find it hard to believe that 4 MC's in a row had the same problem. You sure you're not just seeing residual fluid in the booster from the first leaking MC? Do you have any of the calipers on upside-down (bleeders should be on the top of the calipers)? No leaks anywhere else?

Try this bleeding method after bench bleeding and installing the MC, I've had much success with it, especially on empty systems. Starting with the R/R wheel and working your way from farthest to closest to the master cylinder...

1) Open the bleeder screw
2) Have a helper push brake pedal to the floor and hold it
3) Close the bleeder screw
4) Have helper release the brake pedal
Repeat this procedure until you get clear air-free fluid from the bleeder screw, then move on to the next wheel. Just be sure not to let the MC go dry, keep checking frequently and refilling as needed.
 
Aaron, might I suggest that you go down to the parts store and in the Help! section you'll find speed bleeders. They're a great thing.
 
I find it hard to believe that 4 MC's in a row had the same problem. You sure you're not just seeing residual fluid in the booster from the first leaking MC? Do you have any of the calipers on upside-down (bleeders should be on the top of the calipers)? No leaks anywhere else?

Try this bleeding method after bench bleeding and installing the MC, I've had much success with it, especially on empty systems. Starting with the R/R wheel and working your way from farthest to closest to the master cylinder...

1) Open the bleeder screw
2) Have a helper push brake pedal to the floor and hold it
3) Close the bleeder screw
4) Have helper release the brake pedal
Repeat this procedure until you get clear air-free fluid from the bleeder screw, then move on to the next wheel. Just be sure not to let the MC go dry, keep checking frequently and refilling as needed.
Click to expand...

Everything is on correct.. We have gone over that a couple times. We still cannot figure it out.

Thanks for telling me about the bleeding procedure, but we have already bled the brakes like that too! I have plenty of ways to go at the bleeding. I just need to figure out the M/C leakage problem.

Egg
 
egghead said:
Around three weeks ago, I put my lift on the MJ. Got everything done, ready to drive besides the brakes.....First I thought I wasnt getting brakes because of the porpotioning valve, so i put one on there from a 94 Cherokee.
Click to expand...


Um, when you replaced the MJ combo valve with a 94 Cherokee proportioning valve, what did you do with the extra line from the back?? Or did you eliminate the rear prop valve?
 
We eliminated the rear load sensing valve and removed the extra brake line running back to the rear ...

btw... I'm Egghead's dad.

I hate to admit this, but I will. After all the work and frustration ... and after several of you suggesting this may be the problem, we found the front calipers were not installed on the correct side. This resulted in them being upside down and the bleeders being on the bottom of the caliper.

I am just as guilty of not double checking this as my son ... I could have sworn they were installed properly ... even posted they were!

I have seen several posts where individuals have responded they "have done this" and "checked that" and "everything is correct".

Let me suggest that all of us "really" take the time to check and recheck other's suggestions ... we sure will! Talk about a kick in the head!

Thanks everyone! ... for taking the time to help us out. Despite us feeling like dumbasses, the MJ is back on the road.

Les
 
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