unfixable leaking master cylinder gasket

[Rox Crusher]

77 with stock power brake system

cover gasket leaks at small reservior end of m/c

replaced gasket twice.................still leaks

emptied m/c, scraped and sanded rust / gunk off of top surface of m/c, tried another new gasket..............still leaking

installed new m/c.............still leaking in same spot

the only good thing is that I have the cleanest, most well-bled, brake system in the universe

please chime in with any advice you can offer

 

[NYLES]

I had that problem with my 83 vette MC, drove me nuts the fix was small pair of pliers tweaking the outer lip of the cap so the cap doesnt prevent the gasket from being seated completely......5 min fix

 

[crankman]

ok try a large radiator hose clamp i think about 5in and go around the whole thing and snug it up, i have had that problem a while back and it worked.

 

[thegreatjustino]

Silicone

 

[av bronco]

I have the same problem with a new master cylinder, Im researching a master cyl. with screw on lids or a bolt down top.

 

[broncnaz]

usually you can tweak the hold down a little so its tighter and get it to stop leaking. Other idea is let it alone a little time may let the gasket seat in and stop leaking.

 

[Rox Crusher]

Thanks so far

I don't think it is related to mechanical fit of gasket / cover

the old cover was in great shape, not pinching any of the gaskets

I tried increasing tension on hold-down by inserting thin rubber between it and top of cover

the new m/c came with a new cover and gasket so no pinching going on there either

I was thinking it was a pressure issue somehow ?

I forgot to mention that it has braided steel lines off of m/c if that matters somehow

 

[ManTruck]

I chased the same problem for quite a while until someone suggested the hose clamp fix. I have had two clamps on it for about 4 years now without a drop of leakage.

 

[DirtDonk]

I don't think it is related to mechanical fit of gasket / cover

Well, it usually has to be an issue with the seal and cover to some extent. But I see what you're saying with both the old and new covers doing it. Might be a coincidence, but you might also be on to something with pressure.

I was thinking it was a pressure issue somehow ?

You won't normally see too much of a pressure build here, but you can get a pretty good "back squirt" when you release the pedal. I'm not sure what the dynamic is, but it could be related to air in the master cylinder or an un-balanced system, or something wrong with the rear brakes.
What other work has been done (besides the constant bleeding!)?
What level do you fill the reservoir to? Does your gasket pop down so it extends into the small reservoir? That might be pushing fluid up to the top too much and making it more prone to leaking.
Just kind of grasping at straws here, but enquiring minds need to know. You know?


I forgot to mention that it has braided steel lines off of m/c if that matters somehow[/QUOTE]

Shouldn't matter. But what else was done along with the lines? Is your system working properly? Can you lock up the rears when you push hard enough? Done a disc conversion for the front? Did you remove the residual pressure check valve from the master in the large reservoir only?
Anything else?

Paul

 

[Rox Crusher]

I have only had it for about 4 weeks now

brake system appears to be stock although I am wanting to change to hydra-boost soon

If I stomp on the brakes the fronts lock up but not the rears but I have been attributing this to the shoes which are soaked with axle grease from bad seals

Tires are only 31" and brakes look to be in good shape

I think it does have something to do with the release squirt from the rears though, as that is the resevior that is leaking

I am filling it about 2/3 to 3/4 full each and every time

;D

 

[wildbill]

Cut a pc. of round stock about 5" long X 3/8" and a hose clamp. Lay the bar on the top and clamp works every time. Have one on the bronco and F250 as they would seap and make a mess good luck. Bill %) ;D

 

[Rox Crusher]

okey dokey...........a big ass hose clamp it is

thanks

 

[DirtDonk]

If I stomp on the brakes the fronts lock up but not the rears but I have been attributing this to the shoes which are soaked with axle grease from bad seals.

Not uncommon, but if all was working right, your rears would be locking up too. Defintiely a problem if you've got oil on them though!
Sounds like you should go through the system and check for leaks, adjustments, contamination and such. Replace any worn out hoses and check your H-block too. Then bleed the crap out of them to make sure.
Is your "Brake" warning dash light always on? Or is it out completely?

...and brakes look to be in good shape

Uh, other than the possible oil contamination perhaps???

Paul