I posted this today under a new topic: Bleeding Brakes, but here it is again.
Power Vacuum Bleeder: Simple, Homemade, Free
What you need:
Strong Vacuum source (car engine), maybe a house hold vacuum
Tall clear jar with lid
25 feet of clear plastic line (1/4 line comes in 25 ft rolls in the plumbing section for a few dollars), must fit on the bleeder nipple snuggly
An assistant will be useful
Vacuum adapters if needed
Jar setup: The jar will need two snug holes drilled for the plastic line. Insert the incoming line to the bottom of the jar and the out going about one inch. Place the jar between the bleeder and the engine vacuum. The suction flow is from the bleeder to the jar, then from the jar to the engine vacuum. The jar captures the waste fluid preventing it from flowing to the engine. Use common sense and do not allow the jar to fill. Burning brake fluid in your car’s engine may damage the catalytic converter! If that bothers you, use something else that really sucks. The jar ought to be larger than the quantity of brake fluid container. Position the jar so it cannot tip over or it might suck fluid into the engine. I used a tall coffee jar with a plastic lid.
What Happens: This suction-bleeder uses engine vacuum and the pull is very strong – maybe too strong. When the bleeder is open, you will only see streaming cavitations that appear to be air bubbles -- any trapped air blends in. You are looking for a color change of the old to new fluid. First, a stream of milky brown that turns to a clean milky white in seconds. It’s that fast! This is where your assistant comes in handy pouring fluid into the master cylinder. Be careful not to suck the master cylinder into the jar.
Setup and bleeding:
Connect your lines. The incoming line connects to the bleeder (the one that goes to the bottom of the jar). The outgoing line (suction) connects to the engine vacuum – just pick a good vacuum source.
Position the jar so it cannot tip
Remove the master cylinder cap
Top off the master cylinder with new brake fluid to the very top – it goes down quick
Position your assistant at the master cylinder to pour fluid as it is pulled down
Start your engine
Crack open the first bleeder starting with the most distant one until you observe cavitations
Leave open until the clean fluid appears – it should appear milky white in seconds
You might see bubbles at the bottom of the jar; I don’t remember having time to look.
Move to the remaining bleeders
Test brake action -- it should be improved after the first round
Optional, dump out the dirty fluid after the first round
Circle around the bleeders again until the brakes are solid
If the master cylinder goes dry, start again you have just added more air
If there is no pressure or they are spongy, start troubleshooting
Work the brake pedal to make sure the vent hole is open on the master cylinder. It must be open to pull fluid. You might be able to see it on some master cylinders and fluid will squirt out with the cap off. Watch your eyes! It will shoot fluid out some distance!
Bleeding brakes is simple unless you are fighting trapped air. In theory, the trapped air will eventfully make its way up to the reservoir in the master cylinder and escape through the vent hole -- known as a well-designed system. Some systems are, most are not. Some mechanics let the newly filled brake system sit over night so the bubbles float out. If the simplest method of pumping and opening the banjo nipple fails, it is because it moves too little fluid, too slow. The trapped air moves a little, and then floats back. You end up with no pedal pressure or spongy action. After a few attempts of pump-and-release, you will know if you need more. The idea is to move trapped air forward faster than it can move backwards. If the entire brake system were clear as glass, you could see where the trapped air was and position the bike so it flows upward and out the vent. This home made sucker moves all the fluid and air between the master cylinder and the nipple in just seconds. If there is still trapped air, it is trapped in an out-of-the-way reservoir or metering devise with its own bleeder. This could be a metering valve between front and rear brake or antilock devises. The older Yamaha Ventures had a metering valve with a bleeder under the seat somewhere. Trace the lines to locate these devises and bleed them if there is a nipple. If there is any trapped air, this sucker will surely suck it out in just seconds the first time. It’s never failed me – ever.
This method has never let me down on any vehicle, even equipped with complicated anti-lock brakes and I never had to turn my bike upside down yet! If you cannot get the air out and you are sure you have found all the bleeders, then you probably have a more serious problem, such as clogged or pinched line, leaking seals, etc. Power suction leaves no bubble behind. Its one of the best homemade devises I have made for nothing.
A friend of mine once told me he used his engine vacuum to pull a vacuum on his AC. He rigged up his AC gauges to the engine vacuum. He then drove a distance to his father’s home where they added the Freon. I think this is where I got the idea after seeing the prices of expensive vacuum pullers. Being broke is the genius of many ideas.