pstoppani

I have a 2006 Cayman S that has a brake problem that only shows up at the track so it has been impossible to repro for Porsche reps as well as the extended warranty reps. Here is the repro:

- get up to at least 90-100MPH
- press the brakes so that ABS is engaged
- at each pulse of the ABS system felt through the brake pedal, the pedal syncs closer to the floor

If I stay out of ABS there is no problem.

I played with just barely touching on ABS and it always sinks a bit on each pulse, sometime in big jumps.

This has been a problem for over a year now. My friend originally bought this car based on, in part, my recommendation because I've owned 2 Boxsters (2000 S and 2006 S) as well as a 2006 Cayman S and they were all fantastic cars with zero issues. I drove them very hard on the race track without a single hickup.

He took it to two of the local dealerships and to an indie shop and no one can figure it out. I felt so bad about his whole experience that I bought the car because he was sick of it! He missed many track days and lost a ton of money on the car.

I've had it out for several track days and from day one I felt that the ABS was not working properly. After my last outing I was able to narrow it down to the above scenario.

At this point, I wish Porsche would replace this under the original warranty since my friend reported the problems while it was still under factory warranty early last year. This is a very serious safety issue and I think it is in Porsche's best interest to fix this for that reason alone, not to mention that I'm a very loyal customer (I also own a 1997 Turbo and have owned a few others in teh past) and at 49, I still have a lot of spending years in me.

The ABS unit is roughly $3700, which I can afford if I have to, but it just seem wrong that I should have to pay for this given the fault has likely been there since day one... Plus, $3700 is a lot of track days that I could be enjoying this fantastic car instead of worrying if the brakes will work at 140MPH!!

Any thoughts?

PS - Please, note that we've done all usual tests, I run the proper sized tires, Castrol SRF brake fluid, there is no air in the lines, etc.

RollingArt

and Porsche bled the ABS unit using the PIWIS tool?

Renn 951

You might try scanning the ABS system for faults with the Durametric software after replicating the problem on the track. Come in off the track, don't turn off the engine (fault might reset on startup, so the Dealer won't be seeing it) and check the system. I'm not sure on the ABS system whether the dashboard ABS light will come on with ANY fault indication, but I know with the engine DME there are many faults that won't trigger a Check Engine light but can be read with Durametric.

BGB Motorsports

DO NOT REPLACE THE ABS SYSTEM with another system from PCNA, as it will do it again. What have you done to your car in the harness? Anything? our cars have done this since day 1 and once at Mid Ohio in 2007 we freaked out and began bleeding and purging everything. you'll only feel it on pit road when you look for it. it's not broken. it's a flaw in the system but it will ALWAYS be there for you when you need it.

You can replace the ABS entirely for twice the cost of what you're thinking of investing but truth be told, you probably don't need it. Run a poll out there for who has tracked their 997/987 cars with this feeling and you'll be amazed as to how many people tell you they have the same problem.

BGB Motorsports

Unplug the yaw sensor on the transmission tunnel behind the radio and try it again.

pstoppani

My understanding is that the brake bias is messed up with the ABS shut off... Correct?

Still, this is my second 2006 Cayman S and I had a 2006 Boxster S and none of the previous cars had this problem.

I understand why using race slicks would cause ABS issues, but I'm not convinced there is a general ABS issue when using properly sized DOT R-compound tires.

Anyway, we replaced the ABS unit and just waiting for a dry track day; insanely rare this spring...

rosenbergendo

Same issue with by 2006 Cayman S. Pedal would almost go to floor no matter what we did. We bled it, replaced fluid with SRF, new and diff pads and still brakes just were not confidence inspiring. I dont know about the DFI Caymans but the 1st Gen have MAJOR braking issues. I had enough and got a 2010 GT3. The brakes are totally solid in this car as tested by an ex F-1 driver for over 10 laps!

Krokodil

+1. Completely agree with John on this. While the sinking feeling gives you, well, a sinking feeling it does not affect braking performance.

Cheers,

BGB Motorsports

Yes. When the ABS is off or inactive from the factory, the bias is excessively to the front. If you carry any solid brake pressure you will lock up the fronts immediately. My point was about unplugging the Lat G sensor. The newer generation 987.2 cars have repogrammed ABS DMEs I'm assuming for when they added the whole hill/incline brake pressure assist. (knock on wood). No failures, sinking pedals, strange anything, etc.

GT3 has a nice tall, confidence inspiring pedal with much more of a race car like feel to it but some of that is very much achievable by installing a different master cylinder in the car.

pstoppani

The new ABS control unit did in fact fix the brake problem! Nice to have working brakes!!!