tarmacrdr

I am glad your brake heat issue is solved. I had the exact same issue but with different pads, they were Yellow Pagid's. After several checks/tests, I have concluded that my issue was due to air bubbles out of the ABS pump system. Right after the bleeding, I had no issues with the system. But, as with your experience after a few laps on the track, I had a very soft and long travel brake pedal. I had to pump twice to build pressure in the line. So my conclusion is this: during the bleeding session, I was not able to get the oil/air bleed from the ABS system. Accordingly, there were no issues before the track event - no activation of ABS. During track driving, as the ABS system was engaged, mixing the air/oil from ABS side to enter the rest of the brake fluid and deteriorate it.

Does this make sense?

cham423

That does make sense, and certain pieces of it line up with my problem, although I think the key difference was that instead of having air bubbles in my "secondary" system (PSM/ABS) I think I just had really old fluid (or even water) that contaminated the rest of the fluid once that circuit was tapped. It could be air too, it's hard to say.

It is interesting that the Porsche workshop manual doesn't require a bleed of the secondary system unless that system has been opened, for example if you swapped out an ABS pump, or if there is softness in the pedal after a normal bleed.

I'd be very interested to see a diagram of how that secondary system is set up, whether the PSM pump and ABS pump are one unit, and how much brake line there is in the secondary circuit and its proximity to the master cylinder. Shouldn't it be "open" to the rest of the system during normal operation? I can't see why it wouldn't be but our symptoms indicate that it isn't.

Regardless, I'd recommend anyone with a PSM/ABS equipped car either manually trigger the pump(s) during a bleed, or at the very least go out sometime when it's wet and get into the ABS or trigger PSM a few times just to make sure that you don't get a soft pedal afterwards.

Butzi 997

Hey Cham, glad your braking is sorted for now. If bubbles were the problem, that's the best simple and easy fix.

I'm just back from a full weekend at Putnam in my new-to-me 997.2 C2 with temps around 90 on Sat with HIGH humidity and slightly cooler (83) on Sun. Saturday as my oil temps hovered just under 250 I got a long brake pedal as well. Like you, the car was still braking and the pedal never went to the floor, but of course it happened going into T1 and caused a major pucker. When I backed off for a few laps it got a better pedal but the system really needed an an off-track rest to come back to normal. Pads are new Pagid RS29s.

Sunday my tech/shop owner/buddy was at the track and I asked him about it. He'd heard it before (they work on countless 911s, Caymans, most everything else, many of them track only cars) and went straight to recommending a GT3/Turbo brake master cylinder. He said guys that are used to GT3s are most alarmed by by the longer pedal and others in the more humble 911s like mine just get used to it because it doesn't tend to get worse since it's not usually a fluid issue. I'd rather not get used to it. Motul fluid is also in my car.

I've know him for years and he's not a salesman or "up-salesman." It's a $400 item from Suncoast, which may be the top of the pricing. TRW sells one for $277, which I'll ask my guy about. Just something to keep in mind if your issue returns on an ***-hot summer event.