Brake Master Leaking Slowly at Res Seals. Problem?
 

So I've got a strong pedal, new pads and new rear calipers, fully bled system and overall good brakes.

The problem: My master cylinder is leaking slowly at the resevior seals and it loses fluid. It takes a few days for the fluid to noticably decrease the level of fluid and is not affected by braking as I've tested with soft, moderate and hard braking.

I'm set to take a road trip next week from NY to NC with a friend and I don't know if I can get the master changed by then because the part is special order at my parts stores. You think I would be okay if I just took a sh*t load of fluid and made sure I kept the res. full?

Brake fluid is a very effective paint stripper, keep that in mind when considering this.

It should be fine, I've had one that seeps for a while, still brakes fine, but it should be repaired sooner than later, I should take my own advice

I have this problem from installing a reman master cylinder and putting my old reservoir in. Mine has been leaking all summer but has not affected my brake feel or my stopping distance. Just check the brake fluid often on the trip. The brake light(the one in the idiot lights that tells you the e-brake is on) will come on if the fluid level drops too low... if that comes on when the e-brake is down just pop the hood and fill up the master cylinder.

Thanks for the advice. My plan is to check it and fill it very frequently because if my sensor fails or doesn't read it until it's too low, I'll get air in the system and bleeding my brakes on I-95, although fun, is not very practical.

I plan on making lots of stops anyways because an 8 hour trip in an RX-7 with a passenger, golf clubs, and no cup holders is a cramped endeavor.

your passenger is your cup holder.

you should be fine, just check it like you said. i make trips with relative frequency up to 6 hours. it's not too bad.

I quote my favorite "you know you own an RX-7 when...":

You have to ask your cupholder what they want to drink.

Thanks for the ease of mind. I was worried I would have to postpone my trip.

If you find a solution to this, I'll give you a cookie.

I've had this leak in one form of another for the past 8 years. I've tried new reservoirs, new and rebuilt master cylinders, replacing the rubber seals and switching brake fluid brands. None have worked and I always have a slow drip. Putting a set of hose clamps around the reservoir to hold it on the master cylinder helps a lot but still does not fix the problem.

This winter I am going to totally eliminate those seals by buying a new master cylinder and welding a metal reservoir directly to it.

So buying a new cyl. and res. wont necessarily fix the problem? Wtf?

Weld on, welder. Let me know how it works out. For the record, I'm going to be visiting Bruce Turrentine while I'm in NC and I'll see what the master has to say and reoprt back.

Furthermore, I'm quite honored to have Aaron Cake post on my thread. Way cool. Thanks.

Not in my experience. :( I've tried both as well as getting new seals. The hose-clamps seem to be the only effective band aid. If Mazda sells the cylinder and reservoir as an assembly then you might have some luck there.

Yeah, I ALWAYS buy the assembly because it's only 7-8% more expensive and it saves you from this work. So far the one I've gotten from oreillys auto parts hasn't leaked.

Of course go ahead and rebuild your old one too for the experience and understanding of how it works, and keep it as a spare.

If anyone has a way of getting the reservoir off the cylinder, (while it's still on the car) please let me know. I pulled so hard, if I lost my grip, I would have gone through the hood. Can't imagine how it could be on there so tight. And how about putting it back on? Does it go on with as much trouble?

Do you have a part number or a brand from oriellies? I am getting ready to replace my worn out brake master and do not want to have this ongoing problem.

Thanks

I had an idea! Do you think I might be able to stop some of the leakage temporarily if I caulked (spelling?) aroung the selas with some sort of sealant or plumbers goop?

I don't know of any sealants that will stand up to brake fluid for too long. :(

I had leaky seals on mine and I just pried up a little and used some purple degreaser in between the seal and the reservoir and then pushed res back down and zip tied it. It quit leaking then. I guess the trick is to get the rubber clean then form the seal.

That makes sense. When you pried up the resevoir, did it drain a lot of fluid? Would it be possible to clean the seals without draining the resevoir too much, allowing air into the system? The zip tie scenario sounds like it will help some and I'll definitely give it a try.