Chevrolet Nova Forum banner

74 Drum Brake Master Cylinder

2656 Views 6 Replies 3 Participants Last post by  Tims74
I have a 74 coupe with drums all the way around. I can't get the brakes to build pressure at any wheel. Tried bleeding, but nothing comes out the fitting, not even air. Suspect the master cylinder and was going to swap it out. Went to the parts store and they had one in stock, but when the lady brought it to the counter it looked completely different from the one on my car. Mine has a 1/2" bolt that holds the cover on, but the one they had had a flip bail that held the cover on. Are these interchangeable? I could not remember how many lines mine had when I was at the parts store. If they are the same, can I use the one they have?

1 - 7 of 7 Posts
It sounds like the one on there is the wrong one. It should have the one with the bail on it.
Thanks for the reply. I purchased the one with the bail on it. The connections appear to be the same as the one on the car, so it should work with no problems. I did read another post from someone on here who had a 72 and went to get a master cylinder for it and had the opposite thing happen. He had one with a bail on it and was given one with a bolt on cover. I wonder if it was some sort of factory thing.

One other question. Do all Nova's have the box underneath the master cylinder that the lines feed into? If so, what is it for? Is it a proportioning valve of some kind? I have not seen one one like this on a car before and was wondering what function it serves. Only thing I could figure is a prop valve to send the fluid to each wheel cylinder.


And the dilemma continues. I purchased the master cylinder and it went on with no problems. The lines were in the same location as were the bolt holes. However, I still can't get pressure at the wheels. What could be the cause of this? Could there just be that much air in the lines? If so, what is the best way to bleed it out and how long should it take to get fluid to the wheels?

The way I bleed them is to start at the wheel furthest from the master cylinder and loosen the bleed valve. I have someone push the pedal to the floor and hold it while I tighten the valve. Then I have them let the pedal up and repeat the procedure until I get a solid stream of fluid with no air bubbles. When I loosen the bleed valve, nothing comes out, not even air. Am I doing something wrong????


Tim..Did you bench bleed the MC before you installed it on the car? I have used the method you are using for bleeding for years. However, I decided to read the manual. It states to start the bleeding process at the wheel closest to the MC. If you didn't bench bleed, that is the first thing you need to do. If you did bench bleed, loosen each line as it goes into and comes out of the distribution block to check flow. It should be a process of elimination from there. If fluid is coming in and not out, there is a problem with the valve. Good luck.
That 'distribution block' under the master cylinder.... does it have a small rubber boot at one end (usually the end facing forward)? If it does, it's a proportioning valve, not just a distribution block.

To properly bleed the brakes with a proportioning valve installed, there's a small button under that rubber boot that needs to be pushed in and held in while bleeding.
If it doesn't, and all it has are the brake lines and one wire electrical connection, it's simply a distribution block to distribute brake pressure properly to the rear to keep them from locking up before the front brakes.
I'm not sure a drum brake car will have a proportioning valve though.

The master needs to be bench-bled completely before bleeding the rest of the lines. Keep fluid in the master at all times while bleeding it, then just keep an eye on it during brake bleeding.

Check this out....
See less See more
I bled the m/c before installing it. At least I call myself bleeding it. It built up good pressure with the plugs in place. When installed on the car, I can loosen the lines and it shoots fluid out. I also loosened it where the lines go into the distribution box and it shoots fluid out there. I can hear the front brakes operating a little when someone pumps the pedal, but it is not building up pressure. I guess I just need to keep trying to bleed the air out of them.

Also, it appears that it is a distribution box underneath the m/c. There is a line coming out of the front of it that runs to the front left wheel. There is no button on it anywhere that can be pressed.

I will start with the front left wheel since it is closest to the m/c.

Thanks for all your help.

1 - 7 of 7 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.