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post #1 of (permalink) Old 09-20-2003, 09:54 PM Thread Starter
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Help! Master cylinder lid leaking

I just got the rear discs and 1 piece shafts installed on my 84 CJ7. I bought the brake kit from stainless steel brakes, despite the horriable instructions I got them together. I have been trying to bleed the brakes and my master cylinder has been leaking like crazy all around the lid. I tried a different lid and bent the retainer bar so it would be held on tighter all to no avail.
Another problem is since I still have the stock master cylinder I am having to double and triple pump the brakes (dont worry, I am not driving it like this). would this cause the lid to leak somehow with all the pumping of the brakes?
Third, when I try to bleed the rear lines it comes out foamy and white in color. I realized I may have mounted the caliper brackets wrong since the bleeder screw slightly faces down. Chock that up to the bad instructions too, one part of them told me to have it face up and the other said for the screw to face down ??! Should the foaming go away if I bleed the lines with the bleeder screw pointing up?
I plan on getting a mid 80's corvette MC tomorrow to help the problem a bit, but any help or ideas would be great, thanks.
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post #2 of (permalink) Old 09-20-2003, 10:06 PM
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Re: Help! Master cylinder lid leaking

Bleeder screws need to face up. If it isn't possible then you must remove the calipers from their mounts to bleed them. Do you have power brakes? If you do then I recommend the master from a '79 Firebird w/4 wheel discs. What calipers are you using on the rear? Try to solve the bleeding problem before you purchase another MC. You will only make it harder on yourself by introducing another variable. Make sure the brakes are completely bled and working to their maximum ability before you decide to make any changes. If eevrything is bled and you still have a bad pedal then replace your current MC. I have 4 wheel discs on my Scrambler and I was chasing my tail for 2 weeks trying to solve the problems. I only made things harder by swapping parts many times.

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post #3 of (permalink) Old 09-21-2003, 06:16 AM
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Re: Help! Master cylinder lid leaking

Yep, you need to bleed your brakes. You've got air in the system. You have to pump the brakes to get enough fluid to compress the air bubble. Your master cylinder is leaking because, when you release the brakes, the pressure of the compressed bubble pushes the fluid back to the master and causes the fluid to squirt up enough to hit the bottom of the lid.

Get the bleed screw to the top of the cavity in the caliper and bleed the bubbles out.

You don't need a different master cylinder. The bore needs to remain the same for the front brakes. The only difference is that the wall to separate the reservoirs is centered to make them both the same size for 4 wheel discs. Discs use fluid to push the pucks out further as the pads wear and the level in the reservoir drops. Drum brakes have an adjusting mechanism so don't require the excess fluid so the reservoirs were not divided equally with the disc/drum combination.
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post #4 of (permalink) Old 09-21-2003, 06:27 AM
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Re: Help! Master cylinder lid leaking

Did you lose the diaphragm that goes between the lid and the MC?
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post #5 of (permalink) Old 09-21-2003, 12:18 PM
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Re: Help! Master cylinder lid leaking

By chance, when you pull the lid off the master cylinder, does the lid gasket look okay or is it all shriveled up and deformed. If deformed, somehow you got contamination from a petroleum based product in your brake fluid. Happened to me on a new installation, don't know how, but had the same problems you're having. It only takes a few drops of something to mess it up.
post #6 of (permalink) Old 09-21-2003, 04:27 PM
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Re: Help! Master cylinder lid leaking

It sounds like you did NOT bench bleed the MC before you put it on. With out doing this you will be trying to bleed all that air for quite some time. Pull the MC off put it in a vise to hold it and hand bleed the MC of all air then reinstall.

Next make sure the bleed ports are level or facing up at a angle. pointing down is NOT the CORRECT position. Fill the MC and open all the bleed ports, monitor the rate the fluid drops and continue to fill as it does drop. check each bleed port and whn you are satisfied that that port is running fluid close it off. Do this with all 4 ports.

NOW it is time to bleed the system. Make sure the MC never gets low on fluid through out this procedur.

OH the for days of the power bleeders. [img]images/graemlins/grin.gif[/img]
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