John S Posted July 7, 2014 Share Posted July 7, 2014 I hope someone can help me I with an issue I have with the master cyl., maybe you have had same problem, here goes. My top cover leaks and now I have to refinish brake booster for the fourth time. Here's what I have done. replaced master cyl twice, adjusted bail holddown numerous times tighter and looser, do not want to get it too tight. replaced top cover gasket twice. After all that still leaks. All I can do now is put light coat of silicone on top cover and seal it down. I am clearly frustrated as bleeding brakes and painting booster takes time. Any advice would help, any ideas? Master cyl tilts back it is not level. John S Quote Link to comment Share on other sites More sharing options...
stangeba Posted July 7, 2014 Share Posted July 7, 2014 All of our first gen Monte Carlo's have master cylinders that tilt back. I have never had a leaking problem and still have the original master cylinder that I rebuilt 27 years ago. First thing, I never overfill it, stop when it is ready to overflow at the back. Second, I switched to DOT 5 so if it ever spilled on my paint, no paint removal. Perhaps the lid / master cylinder combination are not a perfect match? Lid made in China and Master made in? Good luck and let us know what you find. Bruce Quote Link to comment Share on other sites More sharing options...
John S Posted July 7, 2014 Author Share Posted July 7, 2014 I'll look close for manufacturer got from my local NAPA store, going to talk with them again tomorrow. So far they don't think I'm nuts yet. probably since the leak trail is obvious. John S Quote Link to comment Share on other sites More sharing options...
wallaby Posted July 8, 2014 Share Posted July 8, 2014 It's not uncommon to have an internal leak past the piston seals inside the master...the result is that over time, one chamber tends to get low while the other overflows. You could also get the same result if your piston-to-pushrod clearance is too tight. (There should be a bit of slop in the pedal before it starts to push on the piston). What happens after you push on the brakes is the piston fails to return enough to uncover the tiny holes in the bottom of the reservoir. As your brakes slowly relax and push the fluid back into the reservoir (as they should), one chamber is not letting the fluid return so the fluid bypasses and returns to the other chamber. Â I've seen this with masters that had the return holes drilled in the wrong place, or rebuilds with the wrong seals, or just too tight of an adjustment on the pushrod clearance. Anyway, I'd bet that the master itself is the problem, and not the gasket assy. Â Many of us have experienced the "fluid dumps all over whenever I remove the cap" syndrome. It's that slow internal leak that causes it. Quote Link to comment Share on other sites More sharing options...
John S Posted July 27, 2014 Author Share Posted July 27, 2014 After some time waiting to get parts I think problem is resolved. Bought new top cover, new gasket and bail wire. New gasket seemed to be slightly firmer than the one that came with master cyl and the others that I got from NAPA. Drove car for a week with no leak. Take one more ride then it should be safe to repaint brake booster again. I worked in auto business from 1978 to 1989 before there was the influx of aftermarket parts that there is now. I guess it's a learning experience. Thanks for advice. John S Quote Link to comment Share on other sites More sharing options...
John S Posted July 28, 2014 Author Share Posted July 28, 2014 New cover and matching gasket solved problem Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.