The Stovebolt Site Forums The Shop Area Driveline Brake bleeding

I have a 1941 1.5 ton with a new master cylinder rebuilt by white post.. I put it in, can’t get the pedal firm. I am able to get fluid at both back wheels, and right front. Left front has nothing coming out. I used a vacuum bleeder on left front too and nothing changed. All was working fine before rebuild, rebuild was for the seal where the threaded end extrudes from the MC, slow leak there over time.


What would cause the left front to have nothing come out, wheel cylinders are about 5-8 years old at most.. not saying a hose isn’t bad, just find it odd that nothing was present before the rebuild. Is there a proportioning valve on these?

The pedal won't be firm if you don't get the air out of alll four corners. You could have gotten some debris in the line when it was apart and that is blocking that side.

I would start by completely removing the bleeder bolt from the left front slave cylinder. If fluid comes out, get a new bleeder bolt and see if the issue is fixed.

Next, unhook the left front soft line from the slave cylinder. Do you get fluid out? If so, the issue is with your slave cylinder. Clean, rebuild, replace as you see fit. Check to see if the issue is fixed.

Next, unhook the soft line from the hard line. If you don't get fluid here, it is the hard line or the MC. I don't have a 41 FAM in front of me, but I believe both front brakes share a single hardline/port so the issue is likely downstream of that.

Jack up the truck and tighten all of the shoes until you can barely move the wheels by hand. Huck brakes need both shoes per wheel tightened up.
Bleed the brakes in the normal, conventional way with a helper.
You are likely running out of piston stroke in the master cylinder before enough pressure is achieved to purge the wheel cylinders.
This is a very common problem.
Once you have a firm pedal, back off the shoes as per The Book.

I managed to get the pedal back to norm by just using the conventional methods. Still have very little coming from the front left, did get some into the bleeder hose and cup with a press on the pedal. I suspect the brake hose had failed internally. Will work on checking that sometime soon

The left front hose would be my suspicion, I replaced every bit of hard line and hoses before attempting to bleed.

Got the hose off, looked at the parts manual and retrieved a GM number of 476719, when I go to Napa and use their number UP 4497, the part comes out and is shorter than the one I took in. It is entirely possible someone put this hose in years ago when the Internet was not a thing and parts were hard to find.

Does anyone know if the 476719 definitely would fit a 1.5 ton from 41-42? If so, I will buy what they have at Napa. Was reluctant to take them with me, seems that I could probably make it work, but the old ones fit nice and certainly didnt rub.

By the way, this hose is the issue, I cant push air through it.

I would take the original with me and match it, longer length wouldn't hurt.

4497 fit well, this project is all done! Napa also sells a 6560 hose, around 18’’ same specs, would have worked well too, but less common and much more expensive.