I've been having a battle with the brakes ever since I bought the Porsche. I knew they didn't work well before buying it, but figured all it would take is bleeding some trapped air out. Well, when I got her home, I find out one of the bleeder screws is broken off. So that explains why the spongy brakes hadn't been fixed. The next problem was finding the correct bleeder screw replacement. Then to get the broken one out I had to heat it with a torch, which required rebuilding the wheel cylinder.
Okay so I had that all done a while ago and never had a chance to finally bleed the brakes. Well I finally got to it a week or so ago and can't get it to work. The way it normally works is you push down the brake pedal to build pressure in the brake lines, then crack open the bleeder screw and let the air bubbles flow out. You keep doing that until it's all fluid and no air coming through the lines. I had my wife pumping the pedal while I worked the screw open and closed, and to my dismay there are only spurts of air coming out and no fluid. I finally get the idea that maybe the cylinder is dry and leaking and needs to be primed, so I take it out again, fill it up with brake fluid and get it all lubricated and put it all together. Still nothing but puffs of air even after pumping 50 times or so.
A week later I've tried a few other methods of pumping the brake with the same results, but now a friend has lent me his vacuum bleeder. Basically, this thing works backwards of how it works when you pump the pedal. You draw a vacuum on the outside of the system, crack open the bleeder screw, and that's supposed to pull fluid down from the master cylinder into the brake lines. Still no luck. Just air!
Then I get a brilliant idea. The only other way I've heard of bleeding a system is to use a power bleeder. This works by using air pressure to force brake fluid into the lines and gurgle out the master cylinder. Too bad these cost $90 at Auto Zone. But I've got a plan. I take the tank from the vacuum bleed kit and fill it with fluid. Then I hooked one hose up to the bleeder screw and the other end I plugged with a nozzle from my air compressor. I set the regulation to 20 psi and let her rip! I got my wife to keep an eye on the master cylinder reservoir so she could warn me if I created a geyser. She looked a little worried when I put on safety glasses. (shouldn't she just be glad I was wearing them and not upset that I felt I needed to wear them?)
Operation was a little slow, but soon we could hear bubbles hissing through the master cylinder and you could see fluid going in on my end. I had to squeeze the tank from the vacuum kit to keep it from misting all over the place. I also briefly tried 30 psi and that just turned into a mess and I quickly went back to 20. After 5-10 minutes, the master cylinder tank level had risen a little bit, but a check of the brake pedal proved to be nice and solid! I couple more pumps and we were able to get the last remaining bubbles out of the system and I think I'm good to go!