emergency brake over tightens rear wheels

[dave71240z]

On my 71 240z I removed all the rear brake parts to clean and repaint. Since I use the emergency brake all the time it will adjust the the rear shoes up so tight the car will hardly move. What a time to getting the drums off. I dont see anything I did wrong. I know everytime you put on the emergency brake it will adjust the star wheel up to tighten the shoes up. I watch this happen when I have the drum off and someone pulling on the emergency brake handel. What stops it from making the shoes get so tight?

[olzed]

The ratchet adjuster should not turn enough to overtighten the drum when the drum is installed.

It might not be the emergency brake at all, but a faulty master cylinder. I had this on mine where the front brakes were pumping up and not releasing. I replaced the master cylinder.

You could check for this by loosening one of the rear wheel cylinder bleeds nipples. If the wheels then turn easy it would be a faulty master cylinder.

I could be way off the mark here, but it's worth a try.

Brian.

[Captain Obvious]

What stops it from making the shoes get so tight?

What is supposed to happen is that there simply isn't enough travel in the adjuster mechanism to "catch" a tooth on the adjuster star wheel. As you saw when someone else was pulling the handle, there is a small lever that catches on and turns the adjuster gear. But the arm is only able to turn the gear if it catches a tooth. When the brakes are fully adjusted, there is supposed to be such a small amount of travel in that arm that it never "retreats" far enough to get behind the next tooth.

It goes like this... As the shoes wear, the shoe travel increases, and as the shoe travel increases so does the travel in the adjuster arm. The magic occurs when the arm travel is so great that it clicks behind a fresh tooth on the gear and when the lever is pulled the next time, it advances the gear by one tooth.

In other words... What your are describing should not be able to happen. Not saying that it isn't... Just saying that it "should be" impossible.

[EuroDat]

Have you done anything to the brake before this started happening? Like already said, the handbrake will not overtighten the brakes. If everything is working right its just not possible.

Things that could also cause binding rear brakes is missing or damages shoes retainer clips, a distorted drum or a seized wheel cylinder (rust and gunk behind the piston).

I would check the bleeder as olzed described. It could be the master cylinder or proportioning valve sticking. The rubbers can swell up and block return ports and such things as refilling with differant brake fluid without cleaning the system of old fluid. Synthetic and normal brake fluid can cause this, they dont mix.

[EuroDat]

Have you done anything to the brake before this started happening? Like already said, the handbrake will not overtighten the brakes. If everything is working right its just not possible.

Things that could also cause binding rear brakes is missing or damages shoes retainer clips, a distorted drum or a seized wheel cylinder (rust and gunk behind the piston).

I would check the bleeder as olzed described. It could be the master cylinder or proportioning valve sticking. The rubbers can swell up and block return ports and such things as refilling with differant brake fluid without cleaning the system of old fluid. Synthetic and normal brake fluid can cause this, they dont mix.

Chas

[dave71240z]

Some great imformation on how it works. Yes I put on a new master cylinder, wheel cylinders, bleed the brakes with dot5, clean and painted the backing plates and installed new hold down and hardware kit at the same time. I turned the drums also. As someone said the master my not be releasing the pressure off of the rear shoes. Im going to have to drive it a little then check to see if I can turn the rear wheels. Or see if there is pressure in the rear brake lines as someone else suggested. I will let you know if I find the problem. Thanks Dave

[Wade Nelson]

Make sure you don't have parts from the right brake on the left side and vice versa. This should NOT be happening!

[dave71240z]

I don't think you can put the wheel cylinders on the wrong sides. I looked the brakes over real good don't see anything wrong with the return springs or the hold down springs or clips. I put it back together and been driving it with out using the emergency brake with no locking up. When I came back I lifted the car and can turn the wheels with no problem. Also loosened the bleeder screws to see if they where under pressure and they where not. I'm going to try using the emergency brake again to see if will over tighten the brakes again.