Rear brake lock

[titan3c]

Just had new brake hoses installed, and my right rear brake is locking up. Haven't discussed it yet with the mechanic. He is a competent mechanic, but I thought I would see what is said here first. I think this may have been happening before replacing the hoses. This car isn't driven much, but I do remember at times it seemed that I was pulling something.

[raygreenwood]

Do you mean locking up while sitting still or locking up as you start braking?

If its doing this when start to brake...and only on one side.... its most probably either fluid soaked shoes, or a very warped drum (common if they have been replaced with new cast drums), or a combination of warpage and adjustment.......combined with......if its a wagon.....the lack of a brake proportioning unit on the wagons.

And....it can also commonly be air in the brake line copposite the side that is locking up. The air keeps the one side from getting any serious braking....so you keep increasing pedal pressure to get it to stop.....and without a brake proportioning valve the side with no air in it will over pressure and lock up. Ray

[titan3c]

Don't know exactly when it locks up It is noticed when driving. Everything is fine when starting out, but after awhile the engine becomes to labor, and that's when it locks. Yesterday after it cooled down it released on it's own. I didn't check to see if the hand brake movement would release it(forgot that). Come to think of it this is not new----When just recently replacing CV joints and the car was up on stands, and the wheels were installed I ran it to check the CV joints and make sure all was OK. I discovered then that I had this problem. The right wheel was locked-up, and I think I released it with hand brake movement. Yesterday when driving from the shop it locked-up, and I hadn't used the hand brake so it doesn't appear to be a hand brake problem. The brake shoes are practically new, and cylinders also.

This car has the Pressure Regulator for the rear brakes.

[raygreenwood]

You have air or water or both in your lines. You may also have some slight warpage to the right drum and/or a difference in adjusting.

This is common. The shoes are probabapy adjusted slightly closer on the right side....but even if they are not......as the brakes heat up, the shoes expand slightly, the spacercbars expand slightly and abovd all...the air or water expands in that line segment causing the pistons in the cylinder to move.

There can also be some temporary issues with drag if one of your shoe return springs is loose or broken.

This can also be due to a sticking or rusted rear brake pressure regulator (very common). The practical life of these units is about two master cylinders worth. Virtually all of them you will find now are defective. Out of all of my years in working on 411/412....which is 1979 to now....I have only seen two working units on anything I have bought or fo7nd in the junkyard. I have rebuilt all the ones I drove on.....but had to literally have seals made. I used my last set of seals in 2000.
My car will be going to rear discs when it hits the road and I will be installing an aftermarket regulator.

The brakes on 411/412. Are difficult to bleed. They take bleeding, driving for a day or two....and then bleed again. Ray

[titan3c]

Ok, thanks. I just went out to the shop, and jacked up the rear end. I worked the hand brake, and it braked, and released as it should. Then I applied pressure on the foot brake, and the right rear locked up. It is tight, and can't be moved by hand. I'm getting suspicious of the pressure regulator. I haven't pulled the wheel and drum yet to take a look.

[titan3c]

Have you researched yet enough to determine what pressure regulator you plan to use? I will do some more bleeding of the line to the left rear to make sure there is no air or water there. But I'm really thinking it will turn out to be the regulator. This morning when I checked it, the car hadn't been moved since yesterday afternoon. The engine and brakes were cool. I was able to roll it back and forth by hand in neutral. So heat is not an issue in the brakes, and the hand brake is working fine. So, it sure is pointing to the regulator as the problem. I suppose prior to getting a regulator I could rig a "T" connection to see what happens. Just a thought.

[raygreenwood]

[titan3c]

Just learned something. I thought the regulator sent different pressure to the back brakes. Don't know where I got that idea. So----a single outlet regulator with a T to the back brakes is OK. Are connections both male and female available to adjust from the system mm size to npt outlets?

[raygreenwood]

[titan3c]

That's interesting. --------- I just pulled the right rear wheel, and drum, and everything looks normal. I applied brake pressure, and the shoes expanded and stayed put. If I disconnected the brake line from the regulator to the right wheel would that tell me anything? Would that be a good indicator that it is the regulator if the brake releases?

[raygreenwood]

It could be just a sticky wheel cylinder, air in the lines or .....it could even be too much tension or rust between the actuating lever, pin and crimped lockring of the emergency brake.
This same thing can happen when the cross bar or leverage bar near the top of the shoe set....is installed backwards and causing the shoes to sit too close to the backing plate causing them to lodge when actuated.

I would pull off both drums......shoes ....clean everything....make sure everything moves smoothly and is installed properly. Then make sure that the e-brake cables are not binding up in their tubes ....this can cause this as well.

Then re-assemble, adjust the e-brake and bleed the system again. If it still has this problem.....its most likely the regulator. Ray

[titan3c]

Any suggestions on the "dos and don'ts" or techniques in adjusting the brake lines to fit a T connection or new regulator.

[raygreenwood]

That is going to take some tube bending.....and making sure you have the right thread or depth of fitting may end up keeping you from driving.....if it does not fit.

I would not bend the original lines too far......i have replaced a T in a wagon...mwith a regulator a long time ago and remember that it would have really mangled the lines. I believe i left the infeed line unbent, installed the T....and bought at least one piece of line at a flaps and just bent it to fit and kept the old lines i removed intact in case i needed to re-install. That was in tue 90s. I no longer have the car and part.

Have you re-bled the system yet?.....also one other thing to try.......is fo loosen the locknut on the regulator and with an allen key.....back pressure way off.....like about 4-5 turns. Count how many turns and mark it so you can get it back where it was. See if yhat breaks it loose. Ray

[titan3c]

Good idea-----didn't know it had a allen adjustment screw. I see in the manual that it is on the end of the regulator. I had planned to loosen the brake line connection to see what happened, but this is much better.

If this releases the brake what does that tell us? Does that mean the regulator is the problem?

[raygreenwood]

[titan3c]

Well, I've got a story to tell. In the beginning of this problem I stated I just had the brake hoses replaced. There was a weird communication mixup with the mechanic which I won't go into----too long a story. Anyhow I discovered the rear brake hoses had not been replaced. I replaced the rear brake hose, and the lock up problem is resolved.

[raygreenwood]

[Methusela]

I have a dead pressure regulator and plan on replacing it with one of the adjustable units from Summit that Ray recommends -- but I have a question:

Since the adjustable unit won't have a built-in gauge to tell me what psi it's set to, I assume that after installing it I'll need to take the car to a brake shop to have them set the pressure regulator at, say, 570psi...right?

Otherwise, how else to set the thing so that I'll know it's at the right psi?
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lots of VWs, two Panhards, and a sun-baked Nissan truck

[raygreenwood]