After a complete re-do of the brakes on my '65, one of the wheel cylinders leaked a large amount of brake fluid. The brake work included new wheel cylinders all the way around, new brake lines, new front rubber hoses, new shoes, turned one of the drums, cleaned out the master cylinder reservior (new lesson - sediment on the reservior bottom stops it from working right. Who would have thunk it?). The brakes were adjusted with a pretty good amount of scuff. The leak did not happen right away. The car has not been driven because I am in the middle of an engine/transmission swap. The power to go without the power to stop is scary. When I removed the drum to see what was up, it was obvious that the wheel cylinder was at fault. There was a lot of brake fluid in between the metal piston and the rubber donut boot on the side with the parking brake lever. None of lines leaked. The bore in the wheel cylinder looked fine, as did the rubber seals. I happened to have a rebuild kit, so I put it in just in case.

The only thing that looked wrong was the bar running between the shoes for the parking brake was in backwards. The wide end is supposed to be on the side with the parking brake lever, I think. I messed up and put the narrow end on that side. Could that cause the problem by giving the wheel cylinder nothing to push against on the side with the parking brake lever? I used the brakes once or twice with the parking brake cable disconnected (the trans cross member is out). I don't see how that could mess anything up, but it's worth a mention anyway.

If I had to earn a living as a mechanic, I would starve to death. I'm just glad the wheel cylinder did not blow out while driving. God protects the righteous and idiots, too. I leave it to you to figure out which I am.

Tim Dixon
Ellicott City, MD
Learning how car systems work one at a time by doing it wrong once or twice before getting it right.

Could just be a defective cylinder.
Could be one of the cylinder's push-pins isn't aligned to its shoe correctly.
Could be something else...
I doubt it's the p-brake bar.
It could drop out and tear up your brakes, or wear through the hub, but until then, it wouldn't likely be a cause of cylinder blowout. Front drums work sufficiently with no parking brake at all.

Don't know what it looks like on a -65, but on later models there are stops on the brake shields, to prevent the pistons from popping out of the cylinders if something comes loose. If you have these stops, I would think that it's just a matter of a bad cylinder.