My brake reservoir is weeping fluid from around the cap when I use the brakes? The cap gasket is new and I've rebuilt the master cylinder with new seals etc, the spring clip is very tight. It's power brakes and front disks.

I've tried disconnecting the vaccum to the booster and that made no difference. I've just rebuilt the engine and refitted everything in the engine bay, it was all OK before.

Anyone have any idea what might be causing this? I'm running out of ideas.

Cheers.

Seems to be a relatively common problem that drives many to fits. Mine does it too. Seems like some have success with adjusting bail wire, new gasket, etc. Others just live with it.

Did you try lowering the brake fluid level?

Mine does it also.New seal tightened the wire.I have it to just a slight seepage now.I can live with it.Rocky

I had the same problem. It was leaking in the front (new master). The bail wire wasn't clamping very well. I adjusted it and the leak stopped.

Had the same problem. Found out the nice new chrome cover was warped. Tried a new gasket and still leaked replaced it with another cover same gasket and it stopped leaking.

Another common problem is that fluid is being heated from exhaust pipes/hedders ect. causing expansion of the fluid.Running the level slightly lower as mentioned may help.

I have the same weeping MC. NON power disc, tried another MC, same problem again. I thought I was the only one.

Thanks for all the feedback guys, nice to know I'm not the only one!

I have the fluid level about 1/4" from the top, I'll try lowering it. I did find that the new exhaust system I fitted was touching the brass end on the rear flexible hose so I adjusted the exhaust to give an inch clearance but this didn't make any difference. I've also noticed that the master cylinder and booster gets quite hot from the engine heat, but I'm now running cast iron manifolds, before I had headers fitted.

I also noticed that the rear axle gets hot and wondered if this was effecting the brake pipe that's clipped to it. I've checked the oil level in the diff (8 3/4" Suregrip) and that is full, also the wheels spin ok, so I don't think that the brakes are binding?

Is it normal for the axle casing where the diff is to get so hot that's it's too hot to keep your hand on it?

One other thought was whether the brake balancer could be causing the problem?

Cheers.

Is one side the resevoir always low? I ask because this can potentially be a very dangerous condition where fluid is bypassing one of the piston cups and being forced into one side of the resevoir thereby overfilling and eventually being forced out the lid. I've seen this on many rebuilt master cylinders, which are always a crap shoot.

Hi, no both levels remain constant before and after I rebuilt the master cylinder.

Thanks for the info.

Just an update for anyone who has a similar problem.

I rebuilt the master cylinder, fitted a new cap gasket, tried disconnecting the brake booster, adjusted the exhaust system for more clearance from the rear brake hose and still leaking.

Not thinking it would have any effect, I tried making the already tight bale clip a bit tighter by bending it at each end. It was very hard to get on but the leaks have stopped! (So far).

I think the reason it started leaking but didn't before is that with the engine rebuild, I have fitted stock cast iron manifolds in place of the tubular headers I had before and as a result the brake master cylinder seems to be getting hotter.

Thank you everybody for your help.

Brake master heat shield?

http://chucker54.stores.yahoo.net/mascylheatsh.html

Thanks Allen, wasn't aware of these.