Hey guys. I have a 67 with 4 wheel power drum brakes. Awhile back I went to drive the car after it had sit for a couple of months, and I noticed the brake pedal was super spongy. I checked the fluid levels and the rear compartment on the master cylinder was practically empty. So I refilled, reblead the brakes, and drove the car a couple of times. I then let it sit for another month. Went to drive it again. Same thing, spongy brakes, little to no fluid in the rear reservoir, front is fine.

First of all, does the rear reservoir corespond to the rear brakes? I see that the lines go into a distribution block mounted underneath the master cylinder. The rear reservoir seems to be grouped with the rear brake line on the distribution block, as well as the front reservoir is grouped with the front brake line on the block.

I ended up taking the rear wheels off, thinking it could be one of the rear wheel cylinders. After pulling the drums I couldn't see any obvious leaks. However the brakes are pretty dusty and the car has been sitting at least a month or so.

So what should I do? Check the fronts? Clean all 4 brakes and rebleed, drive the car and then recheck the brakes for leaks?

Thanks!

- Colby

Assuming that the rear wheel cylinders aren't leaking or any of the brake lines and hoses then the problem is a bad master cylinder!.....It's leaking at the rear of the master so check for brake fluid running down the power brake booster!

Thanks for the reply Ron! I guess I should clean everything up, rebleed, drive, then examine everything again for leaks, including the MC. I think possibly it has sat too long since it drained the fluid because it's not obvious where the leak is.

Thanks for the reply Ron! I guess I should clean everything up, rebleed, drive, then examine everything again for leaks, including the MC. I think possibly it has sat too long since it drained the fluid because it's not obvious where the leak is.


It's not necessary to rebleed and road test!.....Just fill the master up, install the cap and clean up the booster and the rear of master then pump the brake pedal several times.....Watch for brake fluid running down the booster and remove master lid and check that the level dropped, to confirm, if so, you found your problem!

Most of the time, the problem you explained at the opening of your thread is a rear cylinder leak . They usually don't show up as a big wet spot. If you are not experienced with brakes you won't even notice them leaking (which you haven't) . The way that I would explain it to a novice is with both rear drums off the car, one of them will have DARKER dust. That is the one with the bad/leaking cylinder. I would always change both of them.