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Just got back to the states after one cancelled flight. Amazing that you got your pedal back Rob, I'l try to bleed this borrowed master once more and see what happens. Can some one screenshot me the C2 workshop manual page for bleeding it? I happen to have the C4 workshop manuals and it obviously doesn't have it.
Another thing; I've been cycling fluid once bleeding. Do you think some it it could be too aerated?
Alex - Here is the C2 addendum. The key steps is to use foot pressure to help force air out of the master. I normally bleed just using my pressure bleeder but that wasn't enough.
As for is your brake fluid aerated? I doubt it. I re-used my fluid in this last bleed cycle. I think I pushed 2 quarts through, recycling it multiple times without problems.
Thanks for that Rob. Just to make sure I'm getting this right; this means that I need to depress pedal fully and then open up the master to get some air out? (But not killing master seals) Or just pump the pedal hard a few times with the bleeder open? (But seems that would take air in while releasing pedal). I had initially thought this was just pumping pedal few times hard and then opening up the bleeder later to prevent master from failing.
I had bled the system multiple times with my power bleeder at both the master and wheels. This past Saturday, I bled via pumping the brake pedal 4-6 times and holding while my friend opened the master bleed. We repeated that multiple times until the air stopped coming out. It took approx 10 times and 1 quart to get all of the air out. We then used the pressure bleeder to re-bleed the wheels.
Ok, I'm back to square one. The pedal is still soft after a new cylinder, bleeding and a test drive. The pedal feels smooth and OK, ABS kicks in and so on but the travel feels like 10 cm and the bottom is soft. I will also try the old style method tomorrow with a friend pumping the pedal and see if this helps. It can't be anything else than air?!
Ok, I'm back to square one. The pedal is still soft after a new cylinder, bleeding and a test drive. The pedal feels smooth and OK, ABS kicks in and so on but the travel feels like 10 cm and the bottom is soft. I will also try the old style method tomorrow with a friend pumping the pedal and see if this helps. It can't be anything else than air?!
Thomas - The key for me was using the old fashioned friend pumping the pedal and bleeding the master. It took a long time to get all of the air out but it can be done. I'm assuming it will be the same for you with the 993 master.
Ok, problem solved. I friend pumped the pedal today and one large bubble of air came out after a while. I still think the travel is a liiiiiiiitle long but I don't remember the feeling from October for 100% and my pads are 50% worn and that makes a difference. But now the pedal feels solid. So lesson learned, if replacing the master cylinder....pump the pedal! This also means my used cylinder probably was ok but it always feels good with new parts!
Wow, this is getting my hopes up over here. I just always feared doing it this way because of all of the blown MC stories. Going to try this tomorrow and see how everything goes. I had initially started thinking of the ABS pump being the culprit from some other stories, but on secluded roads if I get enough speed and slam on brakes I can hear the fluids rush and the ABS works properly.
Well, unfortunately I can't say it helped. Bled about a cans worth of fluid but when I started it up it was pretty much the same. Question for those who bled this 2-man way; does the pedal noticeably sink to the floor when bleeding? Mine seems to pretty much be in the same place.
My friend who was pushing the pedal said that the pedal sank instantly when I opened the nipple but the bottom felt a bit soft. Then after while when the air suddenly came he said the pedal fell down another "1-2 cm" and now it was at the bottom and with a solid stop. After some more bubbles the pedal now was OK.
This is nothing like what happened to me. Driver gave a few full pumps and then holds, I open and fluid comes out although not too fast, but the pedal he is holding doesn't really move downward. Which brings me back to the initial question, can it be the booster? Doubtful that it could be the booster check valve.
One thing I forgot to mention is that the pushrod in the booster I bought was missing (which is normally held in by three small plastic tabs), so I took the one out of my old booster, slid it into the master cylinder, and then the master cylinder into the booster. A booster rebuild place said that should be ok since the master is pretty much resting against the booster diaphram inside anyway. I'm just getting exhausted trying to figure all this out.
This is nothing like what happened to me. Driver gave a few full pumps and then holds, I open and fluid comes out although not too fast, but the pedal he is holding doesn't really move downward. Which brings me back to the initial question, can it be the booster? Doubtful that it could be the booster check valve.
One thing I forgot to mention is that the pushrod in the booster I bought was missing (which is normally held in by three small plastic tabs), so I took the one out of my old booster, slid it into the master cylinder, and then the master cylinder into the booster. A booster rebuild place said that should be ok since the master is pretty much resting against the booster diaphram inside anyway. I'm just getting exhausted trying to figure all this out.
Alex - My pedal did the same thing, how many times did you try bleeding? I'm not sure why the fluid comes out the bleed screw so slowly but it did on mine. We kept going and after 10+ cycles, the bubbles stopped and the pedal became hard.
I suppose 1 can of fluid amounts to one cycle, at times there were some smallish bubbles, but others seem like tiny specs. Are you saying that your pedal behaved the same way? When you open bleed screw it doesn't really sink as the fluid comes out?
05-13-2015, 08:35 PM
