Quote:
Originally Posted by radorotrex
I'm reading up on this as I want to do my own brake service. This method uses a pressure bleeder but I've been reading about a vacuum bleeder. Some say that the pressure way introduces pressurized air into the system. This is what I found.
You should not use any sort of bleeder that allows air, especially pressurized air to contact brake fluid. All professional brake bleeders use some sort of bladder to seperate the pressurized air from the brake fluid. You wonder why they cost hundreds of dollars vs what you are looking at. Yes you can bleed the brakes quickly, but you are also adding air to the brake fluid. The air bubbles are small, but carry two side effects:
1. They introduce some additional compressibility into the brake system.
2. They introduce some water, through the air, into the brake system. Brake fluid is highly agroscopic and will take this water.
The best form of bleeding brakes is still the two person job. If that is not available, then you should look at speed bleeders.
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I'm not sure that a pressure bleeder introduces air into the system they way you say it does. Surely if you were introducing bubbles(cavitation) into the fluid that would be the case. Most pressure bleeders even expensive ones just use compressed air to force fluid up a tube and into the master cylinder. This does not introduce bubbles into the fluid. Pressure bleeding is generally better than the two person method because it can be done by one technician and it reduces the chances of o-ring damage by pumping the brake pedal through the end of its travel. In the end any time the master is open, bottle is open, fluid is poured you are exposing the fluid to air with moisture so some will get in.