I have a 54 f-100 with the original drum brakes and manual master cylinder.
It had been taking at least 2 pumps of the pedal to stop the truck so I decided to re-build the master cylinder. I did this without removing the master cylider from the truck. After cleaning out the 50 year old fluid (and mud) I replaced the plunger and check valve. When I went to manually bleed the system, 3 wheels bled some air then a good bubble free stream. I had trouble bleeding the left rear wheel. It seemed like there is an endless supply of air. I get good clean fluid but it is half air. As a result the brake pedal goes the to floor. When I removed the drum from the troublesome rear wheel and pushed the brake pedal the brake shoes move as they should.

When I put the drum and wheel back on the pedal sometimes goes to the floor but sometimes it's OK. There are no leaks in the system and I adjusted all the brakes to just slightly drag. The three hoses (50 years old) look OK and all but one metal brake line is original. I'm almost ready to give up and pay a mechanic to troubleshoot but I'm thinking it might be cheaper to buy a front disk/dual master cyclinder kit because it might cost less than the mechanic.

Does anyone have any suggestions.

 

Did you use a hone to clean up the master cylinder bore? If not you may not be sealing good and sucking air in at the master cylinder.

 

I didn't hone it but it felt smooth.
If this was the problem why do 3 wheels bleed OK but not the forth?
Could a bad wheel cylinder be the problem? Not of them lead any fluid.

 

Try a reverse bleeding system.. you can get them at your local parts store.. and replace the bleeder screw.. most likly its just bad from being so old...

 

One option might be to plug the line to the wheel that is giving you trouble and see if the system will work ok with only three brakes. If it works then you know you have a problem with that line or wheel cylinder. Brakes can be maddening when you can't find the cause of air in the system. That would be cheaper than a whole new system. Still you want brakes you can depend on.

Del

 

Thanks for the suggestions.

1 What is reverse bleeding? Does the fluid acutally go from the wheel to the master cylinder when doing this?

2 How can a bleeder screw be bad?

3 How do I stop the flow to one wheel?

 

1.. Is useing a hand pump to push fuild from the wheel to the master.. This is the perfored way..

2.. A bleeder screw can corrode with time and when you lousen it the seat becomes damaged.. allowing air back in once you close it..

3.. not a very good idea.. the master is set up to push fluid to 4 wheels.. and if you block one you can over load the others and blow out there seals.. Or even the lines..

 

1. Is the bleeder screw part of the wheel cylinder? If I want a new one do I buy a new wheel cylinder?

2. If you pump fluid from the wheel to the master cylinder does the master cylinder overflow during the bleeding?

 

1.. yes it is part of it.. And you can buy a new one if you need to.. bleeder screw itself is cheap..

And yes the master can overflow.. get a turkey baster and remove 90% of the fluid first.. top off of needed after your done.. Dont reuse used fluid..

 

Mike,

don't know if I can help or not ??? one thing I didn't see you mention, but probably knew to do... when you rebuilt the M/C ?? did you bleed it before you hooked it back up ???. You have to bleed the M/C just like the wheel cylinders...

Normal procedure is to attach two short lines from the line ports and curl them back up to the m/c reservoir and circulate the fluid till no bubbles.. if you don't do this, you'll have a hard time getting the air out of the system.

Then bleed the lines... the longest then down to the shortest last. If you do that... don't see any visibles leaks... then sumthin is suckin !!! air that is... I'd suspect a wheel cylinder... a line that can pull that kind of air would be spurting fluid on pressure stroke. But I'd bet on the m/c not being bleed properly first...

hope it helps

John

 

You're right, I didn't bleed the master cylinder but if that was the problem why are 3 wheels bleeding properly but not the fourth?

 

Mikedel
I think you might check the wheel cylinder of the offending brake. I had a similar problem were I would bleed the brakes, as best I could, over time it would suck in enough air that I would end up with that double-pump pedal and would have to re-bleed the brakes again. I got tired of this and found one of the rear wheel cylinders had a small leak, not big enough for brake fluid to show up on the garage floor, but enough to suck air into the system. I replaced it and the brakes have been fine since.
Bruce

 

I think I'll replace the wheel cylinders even though they are only 30 years old.

Is there any difference between the $38 version from mid fifty ford and the $10 version from Advance Auto Parts or Autozone?

 

About $28 and no shipping..

 

One more question. I installed the check valve so that the convex portion was inside the spring. Is this correct or did I install it backwards?