The Stovebolt Site Forums The Shop Area Driveline Vacuum Brake Bleeding Thought

I know about home-built pressure sprayer brake bleeder set-ups. I'm also familiar with the Mity Vac to suck the fluid out of the master cylinder, through the lines, and out through the bleeders. I was thinking about what I could use as a vacuum source without buying a Mity Vac and didn't like the idea of using my shop air compressor's inlet.

What about this:
∙Set up an external brake fluid reservoir, using tubing from a vented plastic bottle to a hose barb connected to a spare MC cap. (It might help to have a little valve near the cap to open and close the flow.) Fill the bottle with about a quart of brake fluid and make sure the hose end is submerged
∙Get a mason jar/peanut butter jar and mount two hose barbs on the lid, making them vacuum tight
∙Run a tube from a bleeder to one of the hose barbs on the lid, putting in an elevated loop so that bubbles in the fluid would be visible
∙Run a vacuum line from the engine (such as the windshield washer) to the other lid barb and start the engine
∙Open the bleeder and use engine vacuum to suck the fluid through the lines from the external reservoir and out through the bleeder and into the jar
∙When no bubbles are seen in the loop, close off the bleeder, shut down the engine, move the set-up to the next wheel and repeat until all 4 wheels are bled.
∙Shut off the valve at the master cylinder and remove the external reservoir. Install the road-worthy MC cap.

Would it work? Think it would be worth pursuing? It should only be about 10 - 15 psi pulling the fluid, so it shouldn't damage cylinder components.

Bill

I think you need to find something more constructive to do with your time!

It seems like quite a bit of work. My preference is for the speed bleeders, just for the ease of use and the relativly cheap cost.

Jeff

I already have speed bleeders! But it doesn't address the dance of moving between the cab and the wheels or having to refill the master cylinder. I'm looking at a master cylinder rebuild job coming up, along with the necessary full system fluid flush, not just a typical bleeding, and want to be certain I've got all air out of the system.

Since no one posted a "you idiot, you forgot to..." response, I'm guessing there isn't a technical reason why it won't work.

Being an engineer isn't an occupation, it is a lifestyle.

Bill

Just be careful how much vacuum you apply.A needle valve would help control this. Too much vacuum and you can actually cause bubbles in the system. I'm basing this on a similar set up we used in a chem lab at work.

I have run in to the bleeder valve threads letting air by, so I just kept bleeding not knowing the system was clean long before I quit! Next time I have to do it, I am going to weld two fittings in a spare MC lid for some hose to hook to. Then do the same in a 1 or 2 quart can. I plan to mount the can or hang it as high as I can in the garage so it has a lot of gravity pulling on it. I can then just open the bleeders one at a time and let gravity do it thing. Joe

A Mity-vac is about $35. How much do you figure your time is worth and how many hours do you think you'll put into building the homemade set-up?

I'm hoping I can drag it out to at least 40 hours, maybe 60 so that I can pull OT at 1.5X. The set-up, after gold plating followed by powder coating, should be in the ~$2500 range if I do it right, especially if I can find an NOS MC cap to butcher up.

'Nuff said, points taken: just because it CAN be done doesn't mean it should.

Incidentally, Wyle E. Coyote is a hero of mine.

Bill

I agree with JoeH. Gravity bleeding works just fine, just as long as you raise the fluid above the highest exit point, being the purpose of using a raised bottle.

I rebuilt the m/c on my 57 I had a few years ago and pumped and pumped and pumped it....never did get it reasonably well bled. I went in for the night, checked it the next day and it was fine, the air bubbles had worked their way to the m/c, being the highest point. I topped it off and had no further problems.

Devin