I recently replaced my 86 Jetta GLI's sticky rear calipers now that I'm good and tired of having no e-brake. If it matters, I let the job stretch over two days. I believe I had one caliper hand tightened together last night but the other's line still unattached draining into a jar. I finished bolting everything together today. No more than about 1/2 to 3/4 cup of brake fluid had drained out of each side by the time I was done.
When I went to bleed the system, I was pushing the pedal all the way down, and noticing that even after I thought I got all the air out, the pedal did not firm up as I expected it to. In fact, if you pushed a little slowly it would still go all the way down. Many short strokes would build up pressure such that the pedal would stiffen halfway down but it would still go all the way down if you kept pushing. I stopped messing with it, and dug up some articles about how you can wreck the seals in the master cylinder by pumping the pedal all the way to the floor like that with an old car whose brake fluid never gets flushed, exactly as I had done. It made sense and I found my local Auto Zone was still open and had a new (rebuilt) master cylinder for $30, so I got it and put it in.
The second time I went to bleed it, I noticed two things: the pedal still goes all the way down (with the new master cylinder, doing this shouldn't damage anything now), and the quick pumping does not appear to build up pressure any more. And occasionally, if I push it all the way down quickly, I hear a squirting or sucking sound, I think in the booster, and the pedal doesn't spring back all the way. If I floor it again it will typically spring back after that.
So I hope the first thing is because there is still lots of air in the lines, even though I've bled a quart or so of fluid through the system and have clean fluid with no bubbles now coming out of all 4 bleeder valves for 3 or 4 consecutive pumps. I hope it is not because the replacement master cylinder has an even more horrible leak than my original one might have had. Can someone give me an idea of how much pumping, or waiting, or fluid, it takes to get the air out after replacing the master cylinder? What is the most effective technique for bleeding the brakes? How can I further reassure myself that the lack of pedal resistance is just air?
As for the second thing, well, I don't know why it would do this -- power brake system? -- so any reassurance that I have not now broken more than I have fixed would be appreciated.
Take the mangles out of the reply address to send e-mail.
Thanks, Peter.