the skunk

Hi guys.
I live in France ,where C1 are not very numerous.
A friend came to me with a 1960 car,imported from the USA ,7 years ago.

Among many other problems,the car suffered from a rear right (passenger side)wheel lock up ,at any speed,,whenever brakes were applied.

The whole braking system had been rebuilt,a few years ago.

Nevertheless,i did replace the following items:

rear drums
rear shoes,hardware kit,wheel cylinders.
front shoes,hardware kit,wheel cylinders.

All these from AC DELCO...

I was pleased with the result: the car was stopping on a straight line,and the were was no more rear right lockup.
Then after 40 miles, of testing ,lock up came back...More and more noticeable...

It was just like i have not done anything on the car.

I took it on a test bench.The forces applied on the right wheel were 2and a half stronger than the ones on the left wheel...

So i took the rear drums off and double checked everything,with no evidence of a mismatch,or a defective part.

The right rear wheel keeps locking up,even with the right adjuster at zero,when the left one is leeching the drum.

Like the pressure was very high on the right and wery low on the left side.

After a while ,the master cylinder began to leak...

I replaced it,with a new unit from ACDELCO.

I thought that i found the flaw ...

The master cylinder was letting air in the brake lines that was accumulating in the rear left one,at the end of the circuit...

But no...
Lock up still occurs.

I re adjusted the front brakes,as i found that the car was not diving enough ...
Lock up again...

After many attempts,and tries, i plugged the right rear brake line... and guess what?

LEFT rear wheel lock up...

I am puzzled and clueless...

Any thoughts?
Thank you for reading me so far.

zangx1

possible rear brake hoses are collapsing under
pressure

A-Snake

Did you replace the brake hoses?

the skunk

Hi , and thank you.

A single rubber hose that goes to the T-block...(looks ok,not old ,has been replaced a few years ago...))

From then on,enough juice to lock the right wheel at any speed,while the left one keeps turning...

The T is not clogged on the left side.

If i plug the right side of the T,then my left wheel will lock up...

So ....

the skunk

Hi,and thank you.
No i did not .
They looked like new...(they may have been replaced 8 years ago)
They do not seem to bulge when pressure is applied.

AZDoug

Rear axle seal leaking lube into the brake drum. It doesn't take much, that 90 weight make brake shoes grab like crazy.

Doug

Frankie the Fink

Do NOT trust the "look" of the hoses; they deteriorate internally and "hour glass" so that fluid may pass one way and not the other, so when you apply the brakes the shoes get pushed out to stop but can't retract...

Change them -- BOTH sides at the same time...

Powershift

If the rear axle seal leaks this will happen in spades. Been there before.

Larry

the skunk

Hi,and thank you.
No axle leak:everything is clean as a whistle.

JF in MI

Amen to that. I had one front hose restricted and the other completely blocked on my '60. Probably from years of sitting. Both looked fine on the outside. Not much else to say except making sure the shoes and springs are in the proper position. After the front hoses try swapping the shoes left and right.

the skunk

Hi,and thank you.

The whole brake system was looking in very good condition;at first glance.
But ,there was this right rear wheel lock up thing...
Overall stopping power was not "convincing",and whenever i pushed hard on the brake pedal,right rear wheel lock up occured,at any speed...
So i checked the rear brake components;
There was no axle leak ,on both sides.
Drums were almost new: no ridge or groove,and "made in Canada".
Brakes shoes were like new.
Springs were like new too.
One the wheel cylinder was not from the same manufacturer.
The rubber hose between the steel line and the axle brake block was like new.

I bled the whole system,and had a test drive: rrw-lock up.
i switched the wheels: rrw-lock up
i switched the drums: rrw-lock up
i switched the shoes:rrw-lock up
i replaced the wheel cylinders: rrw-lock up
i replaced the shoes :rrw-lock up
i replaced the the drums,adjusted the star wheels,adjusted the emergency brake system,and had a look at the front too.

So,the front shoes were still usable,and one of the wheel cylinder was "moist".
I then replaced front wheel cylinders,shoes,springs,and drums,after adjusting the star wheels.

I rebled the system and tested the car again.

It was ok; stopped on a straight line,with no premature rrw-lock up.

I drove the car for a 100 miles,and IT came back:RRW lock up.

I was puzzled.

Pedal was ok: direct and not spongy.
Brakes were not binding.

I raised the car, checked for leaks: no leaks.
I took the drums off: no leaks,no oil contamination.

I switched the drums,and test drove the car.

It seemed to be ok for half a mile,then RRW lock up again.

I had a look at the way the system was operating with half the drum pulled up: it seemed to me that right wheel cylinder was pushing the rods faster than the left one.

I went to a dyno shop and had a test : front was ok,and rear figures were 60 on the left to 140 on the right.

So,i decided to check on the steel lines on the axle,for some kink or clogging of the left side one: no kink,dent,or flat.
I ran a steel wire into it: no clogging.
I took the other line(right) off the axle brake block,to check how the fluid would come out of the 2 holes.

That's when we noticed that the master cylinder was leaking heavily on the brake pedal... Too much pumping for bleeding in very short time...
I thought: this is it! air is getting in ,and gets trapped on the left rear tube ,hence the pressure drop and the non effective braking on the left ,inducing too much pressure on the right...

Got me a new master cylinder,and test drove the car after re bleeding the system.

Guess what; RRW lock up again.

So i took everything apart in the rear system.

I checked and compared the depths of the cups in the pistons,the length of the rods: no difference.
i switched the rubber cups in the cylinders.
i cleaned up everything,and double checked the adjustments.

Another test drive: rrw-lock up again.

I let the parking brake loose on the right side: rrw-lock up.
i de-adjusted the starwheel on the right side ,at zero click: rrw lock up.
Finally,i put a plug in the right outlet of the axle brake block: the right wheel was not locking up anymore,but the left one was...


This morning i installed a pressure adjuster with a ****,and reduced the pressure to the rear brakes by 50 percent.
This is not a durable fix,but i need the car to be more driveable .

The first mile was ok,no more rrw-lock up. After a few panic stops,there IT came again,but not as dangerous as it was before...
I do not understand why i can't lock up the front wheels...

So any idea?

This thing drives me nuts...

JF in MI

Once I replaced my front hoses I could lock up all 4. As dumb as this may sound; try swapping side to side the rear shocks. Seems like you've tried everything else.

the skunk

Hi ,and thank you.
So i will change the front hoses.

Interesting about the shocks.

When i push the brake pedal hard,the nose of the car dives on the left and the rear right rises...
(This afternoon,after noticing this "behaviour" of the car ,i put 140lbs in the trunk ,to see if this would change something to the lock up: did not.)(but the tank was almost empty...)

JF in MI

After what you described you might also want to try swapping front shocks side to side. You could just be unloading the right rear so much that the tire doesn't contact the road as well as the other side. I'm also not sure I understand the 'dyno shop' thing. Are you referring to a brake skid pad? (I was in a brake specialty shop for 26 years).

the skunk

I meant a place where they inspect and test your car.
Wheels are turning on big rolls,and there is a meter to show what force is applied to stop the motion.(is that a brake skid pad?)

JF in MI

Yes, I think that would be about the same which adds to the confusion. I think it would eliminate the "diving" inertia of the chassis (shock issue) from the equation but who knows.

solidaxel

Did you replace the rear rubber frame to axle hose with a new one?

Westlotorn

I had a leaking rear drum brake cylinder once that did this same thing but when I took it apart to inspect it was obvious, the brake shoe was wet with brake fluid. It was scarry to drive with the rear brake trying to lock all the time.

Maybe I missed it but Several people above recommended new brake hoses, and I agree I saw where you said they were only a couple years old but hoses are cheap and you are deep into this project.

You can also get a Brake Pressure gauge and plug your lines into the gauge and test brake pressure at all 4 corners to see how much fluid pressure you are getting and you would see if the pressure releases quickly as it should when you lift your foot off the brake.

When bleeding brakes be careful not to push your pedal too far, an old master cylinder certainly will have a rough area outside its normal range of motion, if you push the pedal down all the way to the floor you are way past the normal operating range and risk damaging the master cylinder seal or cup. Easy to create a master cylinder failure this way by scratching the cup on the rough surface of the Master Cylinder when pushed outside its normal operating range.

Keep us posted this is interesting.

Mark

the skunk

Hi,and thank you.

No,i did not.
The fluid gets trough it ,normally,it seems.
Would it be defective,bulging or hourglassed,both wheels should be affected with the lock up ,don't you think?.

the skunk

Hi,and thank you.

Good advice,about the master cylinder...

I shot it up,bleeding and rebleeding: a leak occured.
Nevertheless,there was a lot of gunk,rust,inside.
A put a new one in it,and will remember about limiting pedal travel for bleeding.

I'll get some hoses this morning (aviation type),custom made,as these parts are not available over the counter around here...

There may be a mix of different causes to the rrw-lock up...

Suspension and brake hardware...

I'll keep you guys ,posted.