Drum Brakes

Hello. I have a 1964 Thunderbird convertible.

I’m having the Hardest time Figuring out whats going on with It’s Brakes.

It has 4 Wheel Drums.

I’m getting Different Pedal stiffness. One Minute it’s a super hard pedal that grabs High, Or sometimes it grabs at the very end of the pedal travel, with a Very Sticky Brake, The Wheels will just lock up. (it’s enough to throw someone into the dashboard).

Also, it can be a very soft Pedal, with Little stopping power.

And sometimes it works as it should.

When it first started having this Problem I Replaced Everything. Power booster, All new Lines, Master cylinder (Twice), Wheel kits w/ rear Cylinders. Rebuilt Front Cylinders. Everything is New.

I’ve bleed the Brakes Multiple Times. I haven’t seen any leaks (as before the rebuild).

I’ve run out of Ideas and any help on this would be Appreciated So,So Much!

Thanks in Advance for your Time

My dad owned a '65 T’bird when I was in HS. It had disk brakes on front and drums on rear. Perhaps this was an option, but I thought that era T’bird had disk brakes on the front. Are you sure these are all the original and standard brake parts?

With drum brakes you have a front shoe and trailing shoe. I remember doing my first DIY brake job on a '67 Mustang and not knowing you had to put the shoes on properly. I had very erratic brakes until my brother asked me if I knew the front shoe from the trailing one. Since I said no, he said take it all apart and pay attention and it solved my problem. The front shoe is sometimes a bit longer than the trailing shoe. Check with your parts supplier if you don’t know which is which.

Uncle, I see why you got confused, the trailing shoe is the longer shoe, not the leading shoe.

Grey Rider, the problem with your brakes might be between the booster and the master cylinder. You are going to have to find an old service manual that covers this era car to get the instructions on the correct rod adjustment. Power drum brakes were always touchy because drum brakes work just fine without a power booster.

If you can get a master cylinder for the non power brakes, you will find them much easier to live with, but you might also have to get a new pedal assembly too.

Oh one other thing, check the vacuum hoses and the check valve to make sure there are no leaks there. You may have a defective check valve and that could cause all your symptoms as well. The check valve is in the vacuum line between the booster and the intake manifold. Also check the port on the intake manifold for crud build up.

Thanks to both of you for your responses,
Keith I agree with you it would seem to be either the Booster/Master cylinder or the Vacuum.
I’ve replaced Both the Master cylinder and the booster. I would think if the Rod isn’t the right length, It would give either a long pedal or a Short one.
I’ve checked the Vacuum and it has good Suction. I wonder if it’s Possible to have too Strong of a Vacuum ??

When the brake booster was replaced, did it include a new check valve?


Yes, but it could be bad.The First Master Cylinder, which came with the Replacement Power Booster was defective. I’m going to check that, along with finding out the Correct Vacuum pressure.

Thanks, a fresh view point sometimes finds the Problem and I’m hoping that’s it !!

Are the brakes properly adjusted? How did you adjust them?

The vacuum will always be about the highest intake manifold vacuum. Here is a quick way to check the check valve. Pump the brakes a few times with the engine running to get the feel. The shut off the engine and pump the brakes three more times. The first time, the pedal should feel the same, the next two times, the pedal should be harder and not go down as far.

If the first time, the brakes are hard and high after shutting off the engine, the check valve is bad, or installed the wrong way, but I don’t think that it is the wrong way or the brakes should never have power assist.

The rod should be adjustable and there is a procedure to adjust it correctly.

This may be a long shot but…did you have your mechanic check out the brake proportioning valve? When they get plugged up or become otherwise defective they can cause all kinds of pressure problems. I’ve only seen a couple of bad ones but they were causing the brakes to lock up at the slightest touch.