63 Drum Brake Problem

[Steve D.]

My 63 Convertible picks up air over a period of time...

Pressure bleed brakes, Good hard pedal.

Drive vehicle 400-500 miles, pedal gets lower and lower, untill unsafe!

Re bleed brakes, pedal back to hard.

No fluid loss / no leaks / Master restored by White Post / Wheel Cylinders
from Corvette Central.

Any Ideas? Thinking of replacing master, as a test, with aftermarket.

Thanks, Steve

[John D.]

Re: 63 Drum Brake Problem

Steve, A friend of mine had the same problem with his 67. Problem turned out to be his stainless brake lines. One going to the master cylinder was leaking at the connection. We used Loctite 545 on the fitting and that solved the problem. JD

[Maitland S.]

Re: 63 Drum Brake Problem

I had a similar situation on a disk brake 74. A bent flange on the rear axle resulted in excessive runout of the disk. Constant in-out movement of the piston following the disk drew air past the seals to result in a soft pedal. Could an out of round condition of your drum(s) be the cause? Seems unlikely but might be worth looking into.

[Joel T.]

Re: 63 Drum Brake Problem

My 63 Convertible picks up air over a period of time...

Pressure bleed brakes, Good hard pedal.

Drive vehicle 400-500 miles, pedal gets lower and lower, untill unsafe!

Re bleed brakes, pedal back to hard.

No fluid loss / no leaks / Master restored by White Post / Wheel Cylinders
from Corvette Central.

Any Ideas? Thinking of replacing master, as a test, with aftermarket.

Thanks, Steve

Steve;

I assume that you do get air out each time you bleed. As one of the other guys posted, I have heard of situations where air will be introduced via the pulsation of a disc. I suppose that something similar could happen with drums.. so I might check a couple of things up front...

Are your drums true.. i.e no pulsation when you brake.. New drums seem to all be out of round and need to be trued up. I'm not sure if could actually cause your problem but conceptually it is the same as the disc situation.

I would assume too that you are using a good quality brake fluid, DOT4.

If the drums are true and you see no leaks and you are using a good quality brake fluid then I would swap out the master cylinder as you suggest. If this solves your problem I would send your original off to Apple Hydraulics out on Long Island... they did the MC's for both my cars.

My 1963 is a bear to bleed via the traditional pump it up method.. very difficult to even get a pedal... but once it is there it stays... never quite as high as at first. I finally broke down and bought a pressure bleeder.

Good luck and let us know how you make out.

[Harry S.]

Re: 63 Drum Brake Problem

Steve, you can try an aftermarket MC to test your theory. You can also pick up a 63 MC rebuild kit for about $20.00 and rebuild your MC. I'll assume when it was rebuilt the last time they put in a new sleeve, either brass or stainless. The sleeve is probably good. The rubber on the plunger in the master cylinder may be the problem. It is letting brake fluid go by.

Here is a link to view the kit, but they are available in many places.

http://cgi.ebay.com/ebaymotors/1963-64-65-Corvette-Master-Cylinder-Rebuild-Kit-Drum_W0QQitemZ180358443879QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item29fe337367&_trksid=p4506.c0.m245&_trkparms=65%3A10%7C39%3A1%7C240%3A1318

Just ensure it's a kit for the 7/8 inch bore.

[Kenneth S.]

Re: 63 Drum Brake Problem


Ken

[Paul Y.]

Re: 63 Drum Brake Problem

Check inside the firewall where the pedal goes into the MC for signs of leaking also. It seems the simptoms are MC related. Paul

[Steve D.]

Re: 63 Drum Brake Problem

Thanks to all, I now have a couple of ideas...

I do have stainless lines / Drums are good / no leaks at m/c..

Thanks again,

Steve