How to make a vacuum power brake bleeder

From Crankshaft Coalition Wiki

I have tried pressure power bleeders and they can be quite a mess. Brake fluid hurts very bad when you get it in your eyes and will take paint off. Having it pressurized isn't my idea of a fun time. Having brake fluid under vacuum is much more idiot proof.

What you need: -Vacuum pump -Glass jar with lid -Clear tubing -Brass fittings -All this should cost around $20

Contents 1 Vacuum Pump 2 Glass Jar 3 Fittings 4 Use

[edit] Vacuum Pump

You can get inexpensive venturi (need an air compressor to operate) vacuum pumps made for AC work from Harbor Freight. The one I have is just like the first link but is red and had a R12 fitting on it. The vacuum fitting is 1/8-NPT on the other side.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92475 (discontinued as of Aug 2009)

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96677

[edit] Glass Jar

I used an old spaghetti sauce jar, drilled some holes in the lid and put some brass fittings in it. I needed to use washers to get a tight seal.

Jar and lid with fittings http://s36.photobucket.com/albums/e24/Triaged/Misc/?action=view&current=IMG_0490a.jpg

Underside of jar lid with fittings http://s36.photobucket.com/albums/e24/Triaged/Misc/?action=view&current=IMG_0492a.jpg

Jar assembled ready for vacuum bleeding http://s36.photobucket.com/albums/e24/Triaged/Misc/?action=view&current=IMG_0494a.jpg

[edit] Fittings

I used 3 male 1/4-NPT x 1/8 barb fittings, 1 female 1/4-NPT x 1/8 barb fitting, 1 female 1/4-NPT x 1/8-NPT coupler, and 1 female 1/4-NPT 90° fitting. I also put a ball valve on the pressure input side. The valve is needed to control the vacuum.

[edit] Use

Hook up a hose from the brake bleeder to the fitting on the jar with the short piece of hose inside the jar. Hook the other fitting on the jar to the vacuum pump. Hook up the vacuum pump to your compressor. I used a ball valve on the compressor side to throttle down the amount of vacuum.

There are a few issues with vacuum bleeding. First is sucking air around the bleeder valve threads. The solution is to use Teflon (PTFE) tape or Teflon thread sealer on the threads. If some air leaks past the threads this isn't much of an issue as long as mostly brake fluid is in the bleeder hose. Throttling down the vacuum pump also helps.

Be sure to keep an eye on the fluid level in the master cylinder reservoir as it will go down quickly. If you are flushing out old brake fluid use a turkey baster (that will never be used on food again) to remove the old brake fluid from the reservoir. Refill it with fresh fluid and start bleeding.

I didn't have much luck with either Teflon tape, or sealer, seems that movement of the bleeder valve disrupts the seal. I used silicone grease that would move with the valve, due to the use of Dot 5 brake fluid. Maybe lithium would work with Dot 3 fluid. With the 3/8" vacuum hose I was using, I had to carefully regulate the vacuum source to keep from over running the 3/16" brake line, and causing more air in the suction line.