Simon,

Brake bleeding problems are very frustrating. You have plenty of good advice herein and therein lies a solution. I sit my collection vessel on top of a stool a little higher than the caliper and run the bleed pipe uphill as it were. Another little tip is that I use a small ring spanner held captive over the bleed nipple and undo it minimally to avoid inducing air through the threads just as Dr Bob describes. I also worry about knocking the catch vessel over and showering paintwork with brake fluid- ideally use a catch vessel specifically designed for doing this.

 

Brembo bleeders are notorious for allowing leaks around the threads. This is very obvious using vacuum bleeders, but not an issue when you're 'pushing' with power bleeder.

When I refurbed calipers recently I put a few turns of plumbers' PTFE tape around the threads of the new bleeders I installed, and this should reduce or eliminate air leaks at the threads.

 

+1 on that! When I did mine initially I tried to do it with my Mityvac kit and gave up- it was sucking air through the nipple threads. Similarly when my wife was pushing the pedal I would try to close the nipple just before the pedal floored.

 

When I changed my fluid using a MityVac (vacuum bleeding), I got tons of bubbles at first.

I smeared just a bit of silicon brake slider grease around the base of each bleeder screw before I opened it up.
Worked like a charm.

 

It's been awhile, but I thought that I'd follow up with the resolution to my soft pedal problem. I did everything that I could on my own with no change in the pedal, so I bit the bullet and brought my car into a shop just north of Toronto (EU Autowerks) that has a trained 928 mechanic. He confirmed my suspicions pretty quickly that the air was trapped in the ABS module, so to get it out he used the Bosch Hammer to cycle the pump and bleed it. I had no idea that the Hammer could do this, because if I did I would've attempted to borrow one locally. Anyways, the pedal is back to normal and I can finally drive the damn thing. Thanks to everyone for your valuable advice during this process!

 

Good to hear! Because of the plumbing these cars seem to be very hard to bleed properly. I take it you did not try and bleed the abs unit per post 13? I have flushed mine using a power bleeder, but doing the rubber lines soon and a bit cautious about opening up the system again. Has been fine since the flush.

 

I did try it but it didn't have any effect. I guess the Hammer was needed to cycle the air out of the ABS unit.

 

Great read from the OP (I'm dealing with the same issue after replacing all rubber lines on 4 corners with SS versions after motor removal/reinstall.

Also, great advice from all the experts on here. Now, headed out to the garage to see what progress I can make. I don't have a Bosch Hammer so I will try and see what I can do with the ABS unit and also try to find out what the "B" nuts are.. I have also purchased a new MC just in case as I also have a small amount of fluid leaking between the MC and booster when using the pressure bleeder and I'm only at 3-4lbs of pressure.

Great thread, hoping to find the answer. I may remove all the calipers as well to ensure the new flex lines are bot trapping fugitive (funny comment from above) air..

Thanks, Bryan