Pressure brake bleeder set-up, homemade
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Also works on hydraulic clutches.
By now, most guys are aware of how easy it is to make a pressure bleeder from a garden sprayer. Some use air pressure to push the fluid from the master cylinder reservoir through the system. This requires you to keep a close eye on the fluid level so it doesn't run out during the procedure.
Another way is to use a small volume sprayer and pour the fluid into it and pressurize the master cylinder reservoir w/fluid (not air). This means no chance of the fluid running dry- but does mean the sprayer pressure has to be watched and maintained and the master reservoir needs to be drained back to the correct level when done.
I have mixed feelings about saving the brake fluid once it's been poured into the sprayer tank, but I suppose it would be OK as long as the tank was spotless, dry, and the exposure to the atmosphere was minimal. But do NOT reuse any brake fluid that has been left open, or if any old or discolored fluid is allowed to contaminate it- like by siphoning the excess fluid from the master when done bleeding; I would put that into a separate container to be properly disposed of.
I use a rather large (2 gallon) sprayer. I use 10 psi for most systems. The large tank volume gives a good amount of "run time" before the tank needs repressurized. But instead of pouring the fluid out into the sprayer's tank, I leave the brake fluid in the (usually quart-sized) container it came in. I remove the cap and seal from the brake fluid container, insert the clean suction hose of the sprayer into the container and then pressurize the sprayer. Towels are used all around the brake fluid container to support it and keep it from tipping over. And, for cripes sake, if you make a bleeder like this- keep the wand- just unscrew the tip from the wand so you can turn it off and on at will by using the wand control lever. A couple of the tutorials show the whole wand cut off and I believe that's a big mistake.
Another extra master cylinder lid is needed to use for installing a hose barb into so the system can be pressurized. This is easily accomplished by soldering or brazing if working w/a metal lid or by using brass fittings if using a metal or plastic lid. The seal must be used to seal around the edge of the lid but the center can be open so the fluid can fill the master cylinder reservoir.
Once the pressure bleeding procedure is finished, the excess brake fluid can be removed by a kitchen baster or by siphoning from the master cylinder. If an extension is used on the hose barb inside the reservoir set to the correct fluid level, the excess fluid can be siphoned to the exact correct level without any trouble or spillage. To do that, remove the hose from the wand and allow the excess fluid to drain from the master cylinder into a container to be properly disposed of.
Be sure to wash away any spilled fluid immediately, and avoid any contact between brake fluid and painted surfaces- many types of brake fluid can be harmful to paint.
There are several tutorials online, here are a few:
Even though I have a MityVac, I find it too small, volume-wise, to be a very convenient way of bleeding brakes. They can be successfully used, but a big problem is sealing the threads at the bleeders. I have had good results by tightly wrapping a couple turns of teflon tape around a NEW bleeder, tightening the bleeder until lightly seated, then back out one half turn. That way, all the suction is going into the brake system, and nothing will be pulled in around the threads of the bleeder screw.
Click on the link below for more on making a vacuum-type bleeder system: