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I have problem with the rear breaks on my 1972 Volkswagen Super beetle..

When the engine isn't running the breaks work exactly as they should.
But start the engine and pump the breaks just once and the peddle pumps up to become hard as a rock. No give what so ever.
After this happens it is difficult to turn the wheel either by engine power or by hand. Actually you can't turn it by hand.
Now if you shut the engine off all returns to normal right away. With the engine off you can pump the breaks all you want.
Just start the engine again and it’s back to that hard peddle and locked on breaks.
There is no fluid on the shoes and they look the same as the ones on the right side.
I checked the axles and both slide in and out about the same. It looks like this sliding action is to allow for the wheel to move up and down.
I can't see anything else moving that shouldn't move on the right rear wheel.
But I know there has to be something amiss,

It has to be connected to that axle shaft sliding in and out of the wheel.
I looked at both wheels and they appear to be the same in the way they operate.
The left wheel releases after the breaks have been pumped with the engine running.
It's only the right wheel that locks up and stays locked up as long as the engine is running.
What can I look for?

John

It is in your mind. There is absolutely no connection whatsoever between the brakes and the engine. The brakes don't know the engine is running or not. Something else is wrong causing this apparent connection.

How old are the brake hoses? It could be that the right one has swelled shut, preventing the pressurized fluid from returning to the MC.

Ah ha. That why they lock up. I thought of the break hoses but i don't know if they could release the the breaks a s fast but I can't think of much else.
To make it even more interesting, they started to work as they should later today.

John

First Welcome to the STF johnmd. I agree with Bruce2 that you have a collapsed brake line and or lines, unless some one modified the brake system, like with a power booster, etc......
Is this problem only with one wheel? If so lets go to the wheel first with the car jacked up pump the brake to make the wheel seize up. Now unscrew the bleeder all the way. Does the wheel turn? If it does turn pump the brakes again til the wheel seizes up. Next go to the rubber brake line and unscrew the metal line from the tee where it connects to the rubber line. If the wheel is still seized you have found the problem. That little rubber line, but all 4 need replacing. Just a process of elimination. In the last step we eliminated the rest of the brake system being a problem proving the line is collapsed on the inside. Thanks for taking the time to join the STF and post a very good question.

I'' try that once the weather breaks again.
I don't have a grage yet and our winters are bit too cold for that kind of work.
We had a bit of a mild spell and I wanted to see if I could get to the bottom of this problem.

John

Well I'm a bit ashamed but I feel I should tell anyone who was following this thread what the problem was.
First of all it wasn't the back brakes but the front.
Yes the front and that may have told some of you what was going on.
Today I went under the car to have a look see and there was this device mounted close to the master cylinder with the front break line going through it.
I checked and found out that it was a device that would lock the front brakes solid and this would allow you to burn the rear tires right off the car.
Why would anyone want to do something that stupid I'll never know but there it is.
Now to get rid of it.

Thanks to those that responded.
John

What you're looking at is a line lock. I have one on my car also. I can only see it being an issue when your key is in the on position (engine runs and brake lock up, right?), and the Line lock solenoid is activated due to a short or stuck button. Trace the wiring for the LL, and disconnect it. I'll bet your issue disappears.

Thanks for the reply.
I found the switch and now everything is under control.
I sure wouldn't want to hit that switch when I'm driving the car.
I think it would come to a sudden stop.

John

It wouldn't be an issue if you hit the button. It's designed to hold line pressure. Line pressure has to be present by the brake pedal applied. THe way it's supposed to work is you step on the brake pedal, depress the button (you're now holding front line pressure), let off the brake pedal and hit the gas.

I think when I get the time I'll just put a union in the line and do away with it.
It's something I'll never use.

John

That type of thing was once called a "roll control" or something like that. It can be VERY useful for someone who is not familiar with a clutch in a hilly environment. once you set it you can use one foot for gas and one foot for the clutch and you won't roll anywhere until you release the valve.

If there are no leaks and everything is operating properly, I'd just leave it. You might find a use for it someday.

I probably won't get around to doing anything with it for quite a while.
As for helping with the clutch on hill, well I'm retired now but learned to drive standards further back then I care to remember.
If you could leave it engaged for a lengthly period of time it would make a pretty good theft preventer.
But I hear you can't do that.

John

johnmd wrote: If you could leave it engaged for a lengthly period of time it would make a pretty good theft preventer.
John

...and a dead battery. I just can't recommend that one.

Point well taken.

Thanks for the input.

John

Point well taken.

Thanks for the input.

John