Need help PLEASE

[Bill W.]

Im working on a past Duntov winner 63 Coupe. This car has had about 1000 miles put on it sense restored in about 1975. The owner decided to drive it and the brakes were locked up (Drum). I removed all 4 wheel cylenders and the power brake master cylender. All 4 were stuck and full of dried fluid. The master cyl. had been sleeved in the 70s and was still good condition . I rebuilt all 4 wheel cyl. and the master cyl. now here is the problem . We are trying to use silicon fluid .We tried bleeding and could not get any pedal or fluid out. We tried gravity bleed no fluid . We used a vacuum pump and got lots of fluid from the master cyl & all 4 wheel cyl. Still no pedal And now if you try to vac.bleed it nothing comes out. So I seem to get fluid at times when vacuum bleeding other times nothing . I am going to check the master cyl.vent holes and the size of the new seals and maybe give up on the silicone . What do you think?????????? Bill

[William C.]

Re: Need help PLEASE

I think you have a problem/incorrect size piston/seals in the M/C

[Paul J.]

Re: Need help PLEASE

Bill, the silicone is not your problem. Did you use new bleed screws, or did you at least clean them? I don't know what you mean by "dried fluid" but it sounds like you had rust deposits. This may be your problem. It sounds like you may have a partial blockage somewhere. As for not getting any pedal, that usually occurs when fluid slips past the seals in the MC. Since you just rebuilt it, are you sure that the seals in the rebuild kit are right for the sleeved bore diameter? Try taking a line loose at a fitting (any one, or at a wheel cylinder) and run a wire into the line, then carefully pull it out and see if there's any crud on it. You may need new lines.

Paul

P.S. Apparently Bill and I are on the same page, since we were posting at the same time.

[Edward J.]

Re: Need help PLEASE

Bill, Been there and done that, What you'll want to do un bolt the master cylinder from the booster if power brakes, or un bolt from firewall, whats happening is the push rod is pushing the piston slightly at rear of the master cylinder and has positioned the piston between the feed hole( just look in the master and you'll see the piston is positioned between the hole), and will not let you bleed the system correctly.I generally gravity bleed the systems on corvettes I just find it easier to do this because its a one man operation.

Once the M/cyl. is unbolted remove the cover and just start the to gravity bleed the system.Its takes alittle time to start the fluid flowing but once started you can watch the air bubbles surfacing at the bleeder once gone from all four wheels re-bolt the master.

Should also add to make sure the shoes are adjusted properly and slightly draging the drum, This has been a problem before on this on this board.