Brake fluid leaking from caps.

[Username]

Does anyone know what would cause brake fluid to leak from the caps. The master cylinder is new(not reman) the brakes were just bled. I have steel braided lines, and it is NOT over filled. So somehow the fluid is getting through the little slit in the rubber seal and leaking out of the caps. Now at first I blamed it on the wicked hill I live on since the angle of the incline is so steep I thought maybe it was causing it to fill one side too much and leak that way, but it will eventually drain the whole resevoir so I no longer think that's the culprit. Any ideas? Perhaps I got a junk MC? Whatcha got?

[2.216VTurbo]

How did you establish that is is coming from the caps, just the BF residue on the top? Most common palce for the MC to leak is out of the seal and it runs down the booster, that's an easy one to spot because it bubbles the paint on the booster. But I've had one go bad, leak at the seal and BF was all over the place, the caps, the top etc. Big mess. Only thing I could figure was the airflow under the hood was spraying all the rundown everywhere Auto parts store rebuildes are junk, done by kids in a factory China

[raccoon]

i find if its leaking out the caps youve put too much fluid in. but you say its not, are the seals in good shape?

[Username]

I know it's the caps because at first I thought it was the seals in the piston for the booster, because it was everywhere, so I pulled it to check, and the rod inlet and EVERYTHING around it including the seal area was bone dry, so I cleaned the MC and installed it again and bled the brakes then checked it the next day and there was fluid coming from the back cap then the day after from the front cap as well. The fluid is nowhere else other than surrounding the caps and a little on the top of the reservoir. The cap seals are new since the new MC came with the reservoir and caps and yes it is not overfilled. I guess coming up and going back down the hill from my house could kind of explain it, but it runs the thing dry so I don't think it's actually the problem, plus it doesn't do it with my glh-s, so I'm convinced it's something else.

[METZ]

I'm having the same problem on a 90 Daytona with 4 wheel disc brakes. It seems to do it after the emergency brake has been on. I haven't tried to diagnois this yet but I want to change the caps out and see if it still does it.

Bob

[turbo van go]

+1 for me 89 voyager mc was brand new when installed about 5 months ago. 4000miles. breaks work good. fluid is oozing past caps. whats up with that?

[turbo van go]

anyone have any more input on this?

[Username]

Nope, but I can tell you that folding a small piece of napkin up about 2 or 3 times and screwing the caps back down with the napkin under the vent slots on the side of the cap keeps the whole thing a little cleaner. I have to change them every day or 2. I was wondering if everyone else is using the stock MC or a minivan one? Mine's a minivan one and it didn't leak with my old factory unit. Perhaps that has nothing to do with it though...

[mario03SRT]

Same problem here ever since I put in a new MC 18 months ago.

I even got the caps swapped out under warranty. Still does the same thing. I was going to use a NAPA or other major brand MC to stop the problem. The fluid is very corrosive and is bad for may engine bay and Booster.

Marion

[METZ]

Mine was purchased from Advance auto parts. It is a new unit and it's iron instead of the factory aluminum. I can't remember the brand. Right now this car is down with a bad turbo and I have too many things going on to work on it.

[turbo van go]

seems this problem is pretty common. with no real cure.

[minigts]

... but it will eventually drain the whole resevoir so I no longer think that's the culprit. Any ideas? Perhaps I got a junk MC? Whatcha got?

I don't see how the caps can be the issue if the who reservoir drains. If it drains out the entire reservoir, replace that with the old one. Should just pull out and the other one go in.

[Username]

So I found an old MC in my garage and figured I'd try swapping caps just to see if it made any difference. So far it's been 1 week since the swap and topping off the brake fluid and NO leaks. Apparently the caps that came with the new MC were no good or something. One thing I noticed is that the rubber seals in the new caps that leaked would move around quite a bit in the cap(not sure why that would be a problem), and the old caps were nice and tight with no movement. Either way it seems to stop my leak. So if you don't have an old set lying around, spend the change at the yard and give it a try...at the very least it's one more thing to check off the list.

[2.216VTurbo]

So, tight caps=good. Loose caps are bad umkay


BTW Username. GTG at Anaheim Hooters this Thursday Jan 21st, free beer and wings, you in? Or working at the happiest place on earth?

[Username]

One thing I noticed is that the rubber seals in the new caps that leaked would move around quite a bit in the cap(not sure why that would be a problem), and the old caps were nice and tight with no movement.

Just to clarify, the caps weren't loose when I put them on the MC, but when you hold the individual cap, the little rubber seal would kind of slide around in the cap.

[mario03SRT]

AutoZone swapped mine out but they still weep. I'm certain that this is under cylinder pressure. They secure just fine.

Go figure. Crappy reman probably.

Marion

[Username]

It's been a while now and mine's still bone dry, it was definitly the "NEW" caps that came with the unit. Instead of the autozone caps try grabbing an old set from the yard off a dry MC. Probably only run you a buck or so.

[89ShelbyGuy]

It's been a while now and mine's still bone dry, it was definitly the "NEW" caps that came with the unit. Instead of the autozone caps try grabbing an old set from the yard off a dry MC. Probably only run you a buck or so.

Or the five finger discount..

[cordes]

I'm having this same problem. Has anyone experienced success with the ones in the "Help" section at the parts store? Now that I have the BC coilovers and Toyo tires on the Lancer it's sloshing the fluid out pretty badly. I noticed today that I had nearly emptied the reservoir.

[Turbulence]

I would second getting an old set. I upgraded my brakes including the master and when brake boosting the caps would seep. Swapped them out for an old set (original to the car 1985) and problem solved.

Martin
1985 T&C wagon