Topic: Brake Bleeding - Pressure
Last weekend I changed the brake fluid on my Mexi using Motive Products pressure bleeder instead of the MityVac I've used for one-man work before. I'm very impressed: it was the fastest, least messy way I've found to do this job.
Like normal you siphon out as much old fluid from the car reservoir and fill with fresh, but then attach the special cap and hose to the pressure bleeder. You put a qt of fluid in the tank, pump it up to about 10 psig with the built-in hand pump (like a garden sprayer), and it pressurized the brake reservoir and system to that pressure. Then you just open each bleeder in turn and let the fluid run out until clear. New fluid from the bleeder tank goes into the reservoir so you don't have to worry about it going empty and sucking air. At the end of the job you turn the pressure tank so it picks up air instead of fluid, then bleed the last wheel a bit more until the brake reservoir level is down to MAX. Bleed the pressure off the bleeder tank and disconnect it.
By having the entire system under pressure there is no way air bubbles can be drawn in, as with vacuum bleeders. (I had that problem on at least one car.) However there can be a few problems:
Because the reservoir and the lines to the master cylinder are under the same pressure as the bleeder tank, the hoses need to be in good shape or they will leak, as they aren't normally under pressure. Test these lines when you start, to avoid filling the trunk with fluid!
I used 10 psig, which isn't much pressure to move fluid through the whole system, so the fluid bleeds through rather slowly. If you were trying to bleed air through from a master cylinder replacement it might not carry the bubbles through as well due to the slow flow. More pressure would help, if the master cylinder lines wouldn't leak.
You need a cap attachment to fit the car you are working on. I got caps for both aircooled and later watercooled VWs, and there are others available.
Cost - really not too bad, but an aquarium hose and helper are cheaper if you don't have to buy the helper too many beers. With the fleet of cars in my extended family I do this stuff enough it pays to get the tools.
Overall I highly recommend it. http://www.motiveproducts.com/