Brakes....a little help please?

Hi all!

Here's the issue:

My right rear brake shoes are not releasing but the left rear brakes are fine. When the right is locked up I can use the adjustment bolt to loosen the brake shoe and the wheel turns again but when I then press on the brake pedal it locks up again. Clearly something in the right rear brake is not releasing the fluid pressure.

In my 100-6 there is one main metal line going from the master cylinder to a junction and from there a rubber line goes to a"splitter". From that splitter there are two separate metal brake lines - one to each brake. Since the left rear brake is working fine it's not this rubber line that is the problem because that line supplies fluid to both wheels.

I know that usually the culprit would be a rubber line going to the brake that was collapsing or clogged so as to not release the pressure but since in my car those lines are metal tubes and not rubber could the problem be that the brake "wheel cylinder" inside my drum brake assembly is not releasing the pressure?

Or is it possible that the metal line from the "splitter" that attaches to the "wheel cylinder" the culprit?

Has anyone had similar issues and resolved them?

Anyone know how to test the wheel cylinder?

Thanks for your help!

Chet

I had a problem with the sliding brake cylinder on one wheel getting cocked and locking up. Check the wheel cylinder for free movement. I think I replaced the clip that the cylinder slides on.

I'm with Tim. Ive had the samenthing happen. When you backoff the adjuster a notch and then the brake releases, can you put the adjuster back where it was and have a free wheel? I never did understand how people could suggest that a brake line was collapsing when pressure in the line is really trying to expand it. It would have to be very much deteriorated to collapse at the moment of pressure release but yet be able to keep pressure trapped upstream. I just don't get how that can happen. Also, if pressure were trapped in the line backing off the adjusterwould probably not completely release the brake, the piston would just extend a bit more because the shoe had moved.

A line can collapse internally without noticing it from the exterior of the hose. When this happens the piece that has failed (depends on what way the piece collapses) acts like a check valve not allowing the fluid to return and not releasing pressure. I had this happen to a Vette I owned, front right wheel locked up. I loosened the fitting and it released the pressure freeing up the wheel.

Thanks for your replies!

roscoe said:

I'm with Tim. Ive had the samenthing happen. When you backoff the adjuster a notch and then the brake releases, can you put the adjuster back where it was and have a free wheel? I never did understand how people could suggest that a brake line was collapsing when pressure in the line is really trying to expand it. It would have to be very much deteriorated to collapse at the moment of pressure release but yet be able to keep pressure trapped upstream. I just don't get how that can happen. Also, if pressure were trapped in the line backing off the adjusterwould probably not completely release the brake, the piston would just extend a bit more because the shoe had moved.

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When I back off the adjuster it frees up the wheel. When I put the adjust back where it was the wheel is again locked up. So whatever is getting stuck is not "unstuck" and I agree with you that the shoe had moved but the pressure has not been released.

I checked the wheel cylinder for movement and it appears to be solid.....is there anything else can I do to check if the wheel cylinder is ok or not? Or am I now just going to have to dismantle and replace with a new wheel cylinder and hope that's what's wrong?


Chet

Chet, What you are describing is not a stock brake pluming system

In my 100-6 there is one main metal line going from the master cylinder to a junction and from there a rubber line goes to a"splitter". From that splitter there are two separate metal brake lines - one to each brake. Since the left rear brake is working fine it's not this rubber line that is the problem because that line supplies fluid to both wheels.

Click to expand...

The stock system is a steel line from the master to the junction block with the brake light switch and two steel lines going to the front brakes and one steel line going to the rear (there should be no rubber line coming off the junction block) and at the rear end a flex line to the axle and two steel lines to the rear wheels.
In testing for a partially collapsed flex line, you should relieve pressure by cracking the bleed screw but you should not change any adjustment - presumably it was adjusted fine before the problem.
You also say

When the right is locked up I can use the adjustment bolt to loosen the brake shoe and the wheel turns again but when I then press on the brake pedal it locks up again.

Click to expand...

This is the way it should be - you back off an adjustment and the wheel turns free, press on the pedal and the wheel stops..... I am confused because this is the way they are supposed to work.
Again, if you want to check for residual pressure that is not bleeding back to the master cylinder, just crack the bleed screws and see if that relieved pressure.
Dave

Chet

You say that you have checked the cylinder and it is solid. Do you mean it is solid in the back plate? It should not be, it should slide, as the piston moves out and the shoe is forced onto the drum, the cylinder should slide in the opposite direction forcing the other shoe onto the drum. Take the shoes and springs off and gently tap it with a persuader to see if you can get movement. From time to time I find that mine seize up a little and I have to take the cylinders off and clean the parts up, including the back plate, grease them using copper grease and put it all back together again, a real PITA with the pare of clips at the back holding the cylinder to the back plate.



Bob

I agree with Bob, because that is essentially what I did to solve my problem. I replaced the clips and lubed them with brake grease. The wheel cylinder was getting cocked when it tried to slide and got stuck.

Thanks everyone! I will check the cylinder movement as suggested and hopefully that's the solution

Cylinder was the problem - it was frozen. Replaced with a new one and problem solved! Now have to bleed the brakes and should be good to go.
Thanks!

Chet