The Stovebolt Site Forums The Parking Lot Big Bolts Cannot bleed these brakes for the life of me

Hey big bolters, I am in desperate need of your help before they send me to the nut house. I have scoured the internet and forums for any idea on how to bleed these brakes and have poured in days of troubleshooting and bleeding yielding no results.

I have a 1956 4400 with a different rear swapped underneath (manyyyy years ago). I am almost sure this rear is out of a 79-85 c50-c70 truck with the electric shift 2 speed eaton axle.

I do not have a hydroboost as I converted to a conventional booster/dual reservoir setup that has worked great until I blew a seal in the master on a road-trip almost a month ago.

I replaced the master, bench bled the new master and installed it…
then began the many hours used and techniques tried bleeding these what I believe to be Wagner FR-3 brakes.

I have pressure bled, reverse pressure bled, and manual bled as well as adjusted the shoes all the way out, locking the rear wheels. I have also tried backing off the top adjuster to close the top wheel cylinder in order to avoid trapping air but all to no avail. The best I’ve gotten so far is about 15 pumps before I get any kind of pedal for the rear.

I will also add that the entire braking system is fairly new and was working excellent until that seal in the master blew.

I will attach pictures of my setup.
I really need to find the proper procedure for bleeding these rear brakes. Any information will be greatly appreciated!

Thank you,

John

After the seal blew out on the master, what was the repair? I just bled the brakes on my '57 LCF by myself, speed bleeders at the HydroVac #1 & #2, then tighten them and moved to the front wheels with speed bleeders. I have a stock brake system and have great peddle. I think you still have an issue with the master cylinder.

I replaced the master. I recently pulled the master apart to insure I didn’t get a bad “new” master. Everything checked out. Bench bled and installed again with the same issues.

The bottom wheel cylinder in your picture is plumbed incorrectly. The line going to the top cylinder should be on the upper port of the cylinder to keep air from getting trapped in the lower cylinder. Both sides should be plumbed the same way, with the bridge pipe on the top port of the lower cylinder.
Jerry

That makes sense to help expel air out of the lower wheel cylinder. John, are you getting a stream of solid liquid from each bleeder? I have only bled mine manually, right after I rebuilt the complete system and a couple of days ago when I put the front end back together from king pin replacement. Both bleeding episodes have been easy and successful.

Big Bolt John Go to the first joint in your steel line after leaving the master cylinder,with the master cylinder full you should be able to just gush fluid out of that loosened joint ! Master cylinder will lose fluid. If it will do that go on to the next joint same thing. If it wont do that go back and find why that master cylinder wont pump. It should do this even if not piped right on downstream. I take a new bleeder drill thru it tighten into any cylinder,run farm store clear tubing on the floor back around to the open master cylinder lid. You can then circulate fluid getting air out as you go,if you have firewall mount master cylinder will need the aid of a helper who understands what you are doing. just helped my neighbor with this on a 51 ferd even-- took us 45 minutes had a full solid pedal
One other thing that greenish line in the booster picture if that is copper need to change to steel brake line.

Jerry is spot on. With that on lower cylinder full of air, it will compress whenever you mash the pedal. It will never be fully purged of air. There have been guys who installed disc calipers upside down (switched right and left) and wondered why they had spongy brakes. Bleeders on the bottom just don't work at all. Same with that lower cylinder piped backwards.

Jerry, that was a nice catch. I rerouted the lines today to the correct position and did some more bleeding with the same result. The master cylinder is not bypassing, wheel cylinders are not leaking, and the shoes are adjusted tight. At this point I am absolutely lost. No leaks ANYWHERE. I can pump up the brakes about 7 times before I have kind of rear brakes. I will pick up some of that clear tubing like Fixite7 recommended and try that but I have not been getting any more air with bleeding.

Do you have the truck off the ground so you can spin the wheels while adjusting the brakes? All four brakes need to drag when adjusted, then you can go through the bleeding procedure. Spin the wheel both directions while adjusting the brakes, that helps center the shoes in the drum for a tighter adjustment.

It's also possible the master cylinder is just too small- - - -piston diameter, stroke, or both. If one push of the piston isn't sufficient to displace enough fluid to push all the shoes against the drums, all the bleeding in the world won't help. Try blocking off the line to one rear wheel temporarily and see if you can apply the brake firmly to one hub at a time. The original single line MC and hydrovac was probably there for a good reason.
Jerry

X2 and great catch on all this Jerry.

One other thing is there an adjustment on the rod from the booster to the master cylinder? That could be a cause for not much stroke or moving the piston in too far?

Big Bolt John Sounds like Hotrod may be right about master cylinder being to small takes a lot of fluid for the whole truck and gotta provide it in one pump,less really for a solid pedal the first pump. You'll probably have to relax em a little so they wont drag and get hot.

He needs the shoes adjusted very close in order for the small amount of fluid to get them to touch in one pump, if they are loose or worn one pump won't push them out far enough to make contact.

Mike B

Mike B well I just meant within reason,with everything working right if you get on a little slope when you let off should easily roll back. That is how I check mine,if they are too tight you'll smell em like clutch smell.

We're on the same page, by running a small MC he's just going to have to babysit his brake adjustments as there is no room for error...

Mike B