The Stovebolt Site Forums The Shop Area General Truck Talk Leaky Master Cover ?

hello guys, got a question for you, and need some suggestions.

as you might know, back in july of last year i put power dics brakes on my 57. everything was fine until a few months ago, when i started getting a very small leak from the master cylinder cover.
i took it off, cleaned everything, put it back on, and still, after a day of driving, i get a very small amount of brake fluid that will drip out of the cover, down the master cylinder, and onto my driveway.
it is a very very small leak, and dont affect the brakes at all.

so i ordered a new cover and seal, put it on friday, and it still has the small leak.
i dont have any other ideas.

it is not over full, about 1//4" full from the top.
any ideas, or has this ever happened to any of you ?

its a dual master and kit from performanceonline.

http://s251.photobucket.com/albums/...00/?action=view&current=DSC01566.jpg

http://s251.photobucket.com/albums/...00/?action=view&current=DSC01539.jpg

any leaks absolutly drive me crazy, and i would like to fix this some how, but i am ready to just leave it alone and add brake fluid when needed, which would probably be every year, since, like i said, the leak is so small.

oh yea, and the 2 retaining clips are new and hold the cover down really well.

thanks..

leonard

Could it be that the housing itself is slightly out of square?Lay a straightedge across it and check.Also was the mc a rebuild? mabe they machined the surface and it's lower thus not clamping as tight.Just my thought's.Tom

If it has a full bladder type seal it shouldn't leak but if you have air in the system or the rear brakes need adjusting it will shoot a lot of fluid back into the resorvoir when you release the brakes.

There wasn't any need to put teflon tape on the brakelines either. That won't keep anything from leaking. It might make thinks harder to service in the future too,
Scott

its a new master, so i doubt its that, but if i can get a straight edge on that surface next time i pull the cover, i will give that a try.
but i do know the 2 clamps do hold it pretty darn tight.
kind of wish now that i went with the firewall mount conversion also. its a lot easier to get to.

thanks.... leonard

full bladder type seal, meaning on the master cover ? it does have the full type seal with the master cover.
a few months ago my back brakes were way out of adjustment, but i adjusted them, so they should be fine, but maybe i will check the rear drum adjustments once again this week if i get a chance.

thanks for the input guys..

leonard

yes scott, i got some riff for the tape before... my stupidity. LOL.
thanks....leonard

Just a clarification on the teflon tape. It is not needed on brake line fittings, but the tape is needed on any of the adapters that are pipe threads.

Bleed the AIR out of the system...

thanks lonnie and mechanic9.

there shouldnt be any air in the system, when i installed the kit i bled the heck out of all 4 brakes, so i will try the rear drum adjustment again first, but if it still leaks, then i will try to bleed again.

thanks much guys..leonard

Leonard,
Try this, I take it the cap has been for a bit, pop it off and check the gasket surface for a tiny skip on the sealing surface maybe there is a flaw on the master cyl. sealing surface? the gasket should show it.
A properly sealed and vented cap should not leak even with a few bubbles in the system, that is what the bladder and vent are for.
just my 2 pennies.
Tim

thanks tim, i sure will check for defects in the sealing surface. its really kind of strange, since for the first 6 months everythign was fine,a nd now, for the past 3 months i am getting this small leak...strange.
thanks again.

leonard

Had the same problem on a 79 1 ton. I finally took the master cylinder and turned it upside down on a belt sander and trued the top of the reservoir chamber. This was a 6" wide shop sander not a portable belt sander. It solved the problem. Just like yours never a big leak more of a seep.

Jim

wow. amazing bill... thanks for that info.... i dread thinking baout having to pull the master to do that, but iff this little seep leak persists i guess i have no choice.

thanks a bunch for all your help guys.

leonard

sorry, i meant, thanks jim, farmer51....

One other possibility.You evidently have an under the floor mounted MC.You could have it mounted too close to an exhaust pipe,which in turn would raise the temp. of the brake fluid,causing it to expand and seep.

If you suspect that your top edge may not be true, I suggest looking at it with a straight edge and feeler gauge.

dale, i guess that could also be a possibility. the exhaust pipe is not real close, but next time i am driving around i will feel the master and get a feel for how hot it is getting.
thanks...

yes, very strange huh ? i hate leaks, and since everything is new it should not be leaking.
i just checked, and i am running the new prestone synthetic DOT 3 fluid.
does that sound correct ?

thanks guys...

leonard

i used the "high temp synthetic DOT 3 fluid"

http://www.prestone.com/enlarged/in...1&name=Synthetic+Hi+Temp+Brake+Fluid

http://www.prestone.com/products/functionalFluids.php#functionalFluids1

leonard

just one more thought....Could the cast iron be pourous? Like seeping through? Just another guess.Tom

wow tom, i sure hope not...wouldnt think so though..

thanks

leonard