How to pressure-bleed the brakes on a B-van?

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Bill Crowell

Bill Crowell

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Remember how on the early B-van, the brake master cylinder was mounted sideways, and so close up under the body that you could barely get the top off of it?

The brakes on my van have gotten pretty bad. I don't seem to be getting any pressure to the rear brakes, and the pedal is low. I would like to be able to hand pressurize the M/C with my Mity-Vac in order to diagnose the problem, rather than having to ask someone to pump the pedal, but I can't figure out how to do it, due to lack of clearance between the top of the M/C and the body.

I was hoping that some of you kind people would advise me how to pressurize the M/C on my vehicle. Thank you very much.
 
Do you have fluid lines that would allow pulling the master cylinder to accessible position?
I'm just remembering some import water pump job from 30 years ago. Unbolt and shift the master cylinder for workspace.
 
You gave me an idea, redfish. For my purposes I could just tie the Mity-Vac directly into the lines and pressurize them. I don't actually need to pressurize the master. Thanks a lot!

The rear brakes are in good condition and adjusted. The problem is that I'm not getting any pressure to the rear to speak of. It's gotta be either a bad master cylinder, bad or blocked proportioning valve, blocked lines or bad body-to-differential hose in the rear. I would like to diagnose it properly rather than firing the parts cannon.
 
Bill Crowell said:
You gave me an idea, redfish. For my purposes I could just tie the Mity-Vac directly into the lines and pressurize them. I don't actually need to pressurize the master. Thanks a lot!
The rear brakes are in good condition and adjusted. The problem is that I'm not getting any pressure to the rear to speak of. It's gotta be either a bad master cylinder, bad or blocked proportioning valve, blocked lines or bad body-to-differential hose in the rear. I would like to diagnose it properly rather than firing the parts cannon.
Click to expand...

That's no exactly what I was thinking. The master will likely drain with lines removed. Whatever works though. Good luck with it.
 
A friend uses a coleman stove pressure tank. Fills with brake fluid and pumps it up. Made some kind of adapter to connect to bleeder. He pushes fluid from cylinders back to master cylinder. Zero air in system.
 
Tooljunkie said:
A friend uses a coleman stove pressure tank. Fills with brake fluid and pumps it up. Made some kind of adapter to connect to bleeder. He pushes fluid from cylinders back to master cylinder. Zero air in system.
Click to expand...
A thumb pump oil can will work a few times like this also with a piece of 1/4 inch clear vinyl tubing and using teflon tape or paste on the outside half of the brake bleeder threads. I almost always push bleed, it works wonder on a complete brake system rebuild, usually don't even have to bench bleed the master cylinder, saves brake fluid as well.
 
Garrett Ellison said:
A thumb pump oil can will work a few times like this also with a piece of 1/4 inch clear vinyl tubing and using teflon tape or paste on the outside half of the brake bleeder threads. I almost always push bleed, it works wonder on a complete brake system rebuild, usually don't even have to bench bleed the master cylinder, saves brake fluid as well.
Click to expand...

Good tip for when I do a regular bleed job; thanks a lot! For now, though, I need to pressurize them from the front in order to diagnose the problem.
 
I made up a pedal hold down. As a last resort i use it. When i have no helper or he’s an idiot and wont listen.
668CDC4E-49FE-4EB7-A0FB-7D3F0C048C60.jpeg
Pointy end on pedal, push rod down to hold pedal and flat bar against front of seat. Need more pressure, push pedal with foot and lock it in place. Flat bar is 1/4” thick and it grabs rod nicely.
Also good for brake light diagnosis.

It makes for a lot of back and forth, but waiting for someone to come help usually takes longer.
 
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