Quote:
Originally Posted by Mick B
There were some comments advising against using the basic pressure bleeder.
Can these few minutes that the fluid is under pressure really absorb enough moisture to make a difference?
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You will hear many different opinions on this, especially from those selling pressure bleeders. The fact is that brake fluid is highly hygroscopic, meaning it absorbs moisture eagerly. It is the #1 problem with brake fluid in general.
Pressure bleeders take atmospheric air (which has varying moisture content based on the current humidity) and forces it into the brake fluid. I take great measures to try to avoid anything even close to that. If you have completely dry air or nitrogen available, then I withdraw my objection. Most people don't.
The best way (still) is to bleed brakes it manually, which takes 3 people to do correctly. It's ALWAYS best to bleed front and rear systems at the same time, so the master cylinder piston can travel fully without interference from the other circuit, since all cars today use tandem designs. Race cars utilize dual master cylinders, and teams normally bleed all four corners at the same time. I don't have one of those crews at home (or enough 11mm flare wrenches).
Vacuum bleeders don't seem to have any negative effects and can be done with one person, as long as they are watching fluid level in the reservoir!
That said, many people swear by pressure bleeders. I just swear at them, but nobody listens...
Chris