Smoke after track session

[rb14]

Took my 07 manual 987S around (UK) Castle Combe circuit for fifteen minutes. It would be fair to say I hammered the car: the rev-limiter and ABS earned their wages. It was fantastic. The car performed way above my expectations. The only two slight disappointments were that I felt the suspension was a little on the sift side and I couldn't get much grip out of the OEM tyres. Slicks next time.

Well, I say next time. I'm not too sure though. After the session, had half an hour at the trackside cafe. Getting back into the car, turned the ignition on and the fans were still on! Ah well. Presumably it was still a little hot under there. Turned the key, the engine fired right away but horror of horrors, the most almighty plume of smoke out of the rear of the car. Enough that everyone in the pits turned to see what it was. Drove away sheepishly and the smoke cleared quite quickly. No sign of trouble on the gauges, the engine sound or any other malfunction.

Ten minutes down the road, stopped again for about two hours. Wandering around a beautiful village in the Cotswolds. Back to the car, ignition on and...

...

... oh bugger. Fans still on. STILL ON!!! Hmmm, clearly a problem. Perhaps a connector melted and shorted the wires? Don't know. Start the engine and...

...

... oh bugger. Another enormous plume of smoke. Ooooops. We've cracked a cylinder or burst a seal. Again though, no sign of any malfunction. Drove away even more sheepishly, the smoke cleared.

Stopped once on the way home for another coffee and to fill up with petrol. Half an hour later, ignition on and...

...

... silence. No fans. Start the engine and...

...

... the engine started. No smoke, nothing.

Drove home.

Not one single problem or suggestion that there might be further damage since. Nearly a month now.

Good cars these Boxsters.

[Westcoaster]

I have heard that after a particularly hot track session, if the engine is turned off immdiately while still very warm (fans still on), that this will happen.

You did mention in each of the first 2 cases the fan was still running when you got to the car...

Have you asked the dealer?

[wvicary]

Always wise to do a few "cool down" laps before shut things down. Maybe the oil level is slightly over full and even more so with a hot engine after being on the track. Just a stab in the dark mind you.

[rb14]

I think both are right. If I had my time again, I'd definitely use at least two slowing down laps. It might be simply impractical to wait for the fans to shut off. It's very very confined under there and I'd imagine it would take a long time for things to cool down properly.

[Lucky]

What color was the smoke -- white/grey = coolant, blue = oil, black = unburned fuel -- this would help determine if there is anything to be concerned about.

If it was blue or black, I wouldn't worry. If it was white, I would watch things closely... that could indicate a failing head gasket or cracked water jacket.

As a general rule, always let your engine idle until temps drop to normal before shutting down. I drove an air-cooled 911 on track many days over the course of several years and was always careful to ensure it was cooled before shutdown. Those motors cool very quickly, so it wasn't much of a hassle. For our Boxsters, more time is needed to cool them. You may need to let it sit and idle with the fans roaring for 5 or 10 minutes after you return to the paddock even after a couple of cool down laps. Your engine will thank you.