Brakes: 50 Champion pedal goes to floor

[doubledaddy]

I'm stumped. Just replaced the rear axle with a 50 land cruiser axle to get the 11" brakes. All new wheel cylinder. Bled and adjusted all 4 wheels. Took it for a test drive. All was fine for about half a mile. Hit the brakes at a stop sign, heard a pop from under the floor and the pedal went to the floor. Pumped twice and brakes held fine until I released the pressure. Now it always does the same thing. Not leaking anywhere, I pumped it twice and held my foot on it for ten minutes with no loss of pressure or fluid.

I went thru the whole thing again. Used a vacuum bleeder and bled all four wheels until I got clear fluid out of each and readjusted all shoes to drag. Pedal still goes to the floor the first time but never looses fluid.

I seem to remember a problem my dad had about 60 years ago on a old Plymouth. The fluid was leaking around the forward cup in the master cylinder back into the reservoir. No fluid was lost but the brakes would not hold. Not sure of my facts, been a long time. Anyway, if this is the case why would this happen just when I changed the axle. Also wondering if the hill holder could be causing it. Anyone have any suggestions? I'm lost.

[Mike Van Veghten]

It's supposed to, at least once a day..!

Oh, you're speaking of the brake pedal... Sorry, no idea.
I'm in the middle of putting all new brake parts in my Conestoga. LOTS of pedal bleeding, so far so good.

Mike

[jclary]

Besides the pedal going to the floor, the most puzzling thing (and frightening) is the "POP" you heard. I've had brake system "pops" before, due to a hung up wheel cylinder releasing under pressure. Mostly in my driveway, because, I wouldn't take it further until the problems was addressed and fixed.

I'm wondering if your adjustments on the shoes didn't have some kind of bind or glitch that allowed you to bleed the brakes and give the impression all was OK until you actually had to brake under driving conditions. If that happened, and, whatever brake assembly broke loose and traveled further to make contact with the drum...could have been the "pop" you heard and the extra travel caused the pedal to go to the floor to compensate. Besides the brake bleeding, you need to check adjustments on all wheels.

Another thing to look for is the vent hole in your master cylinder cap. Although that can cause the pedal to go to the floor...your description of the problem, how & when it happened, makes me doubt that is your problem. Check all wheel brake assemblies, adjustments, etc. and let us know what you find.

By the way...If you can talk some strong legged assistant into pumping the brakes for the "old fashioned" bleeding method, try that too. I have a couple of those bleeder devices, but still find the old way the most dependable.

[RadioRoy]

So... are you saying that your car now has 50 Champion brakes in the front and 50 Commander brakes in the rear? I hope that's not the case.

If you can pump up the brakes, that usually means the shoes are not set up properly. They are retracted too far and need extra travel, which is why they need to be pumped. Time to take them apart again, or at least perform the mechanical adjustments again, and see if something slid off the eccentric cam.

[t walgamuth]

It also might be an internal master cylinder leak.

[doubledaddy]

Yes it has commander brakes on the back and champions on the front but only because I'm not finished. I have the front king pins and they bolt in with the same control arms and pins. The complete front arms and king pins are interchangeable. Don't even have to remove the control arms. Just remove the upper and lower outer pins and swap the kingpins. Only thing that is not the same is the outer steering arm on each wheel, the holes are larger. I have a welding shop here who can modify the tie rods to accept the commander outer ends.

RadioRoy, you are correct. It feels just like cars I have driven in the 50's that had the shoes worn down and you had to pump them each time you wanted to stop. Long before self adjusting brakes. Think I need to pull the drums off the rear and have a look in the morning.

Let you know what happens.

[Lothar]

So what's the state of your master cylinder? Did you rebuild it yourself or buy a rebuilt unit? Does it have a hill holder? You probably ought to have a Commander-sized master cylinder if you plan to use Commander brakes.

[rkapteyn]

The front suspension on the 1950 cars were completely different between the Champion and Commander.

[BILT4ME]

1) Check to make sure the little bleed hole in the inside of the master cylinder is open and clear. It looks loosk a blind recess in the bottom of the MC but there is actually a tiny hole in it. The master cylinder should squirt a little straight up when you first press the pedal. If not, a piece of tag wire in the hole to clear it should help to bleed it clear.
2) If the rear brakes have the same diameter wheel cylinders as the one that came with you car, you will be fine for the brakes. If they are a larger diameter, then you will not get enough pedal travel because your volume increased too much. You may need to change to the same master cylinder that your new rear brakes came from.
3) I understand the Hill Holders can be tricky to bleed. I personally have no experience with them, but others can chime in.
4) A "POP" under braking indicates something came loose. I would be concerned that a spring came loose in one of the wheels or something is not retracting. I had one recently that the shoe was stuck to the drum and it shoved the shoe sideways in the drum and forced it over the lip on the riding surface of the backing plate and the pedal would always go to the floor . Once I took it all apart and realigned the pieces, it works great.

[RadioRoy]

So what's the state of your master cylinder? Did you rebuild it yourself or buy a rebuilt unit? Does it have a hill holder? You probably ought to have a Commander-sized master cylinder if you plan to use Commander brakes.

Same master cylinder for Champions and Commanders. Wheel cylinders are different between Champion and Commander.

[doubledaddy]

I found the problem. Removed the rear hubs and found the linings on both sides had slid half way around the shoes. The linings came off with just a small screwdriver pushed under the edge. I had them lined by a local shop and whatever they used for glue did not even get hard, feels like contact cement. Needless to say I am more then a little upset. Only good thing, I now have a complete new set of linings. All I need is to get them on the shoes. I have found a place in Fort Worth that has been lining shoes for 18 wheelers and buses for 30 years. They say they can do the job and I tend to think with there history it will get done correctly.

The steering on the 50 Champion and Commander are different but the control arms and inner and outer pins are the same with the exception of the Commander upper arm having mounting holes for the leaver shocks. I have a 1950 Champion frame sitting in front of my shop with everything from the land cruiser installed including the springs. Only thing left is the fabrication of the tie rod ends. Even the steering arms on the Land Cruise spindles are the same length. The wheel cylinders are different but the bore is the same, 1 inch front, 7/8 inch rear.

The rear axle fits but had to use the spring plates from the Land Cruiser as the axle housing is larger. I intended to do this anyway as I am installing the rear sway bar as well. Also the axle pinion housing is 1 inch longer requiring a shorter drive shaft. I had a rear drive shaft from a 51 champion which is 1/2 inch shorter then the 50 and I fabricated 1 inch lowering blocks from solid aluminum bar stock with the axle alignment pin 1/2 inch behind the spring pin. This moved the axle rearward 1/2 inch and every thing fits perfect plus it also lowered the rear 1 inch. Now if I can get the brakes working it should stop a lot better.

[christophe]

The linings came off with just a small screwdriver pushed under the edge. I had them lined by a local shop and whatever they used for glue did not even get hard, feels like contact cement. Needless to say I am more then a little upset.

When I opened the brakes on my GT, I was glad that the linings were almost new but I had to remove them to change the cylinders and clean everything. When I put the first one on the floor (gently), it separated from the shoe! Now, I use rivets again on my brake jobs...

[Son O Lark]

Check your shop manual, but I know on later years, you need to adjust the shoes tight to the drum THEN bleed the system, then readjust the shoes.