2002 C4S Gushing coolant at long idle

My friend had this problem recently and has the dealer and me stumped. The car has been hibernating due to the weather. Every few days he would throw the garage door open and run the engine a bit. The last time he got side tracked and the engine idled for maybe 20 - 30 minutes. When he went to the garage to shut it off he found coolant all over the floor and the radiator fan was running. Since this occurrence the dealer has check the car twice and has found nothing wrong with the car. Certainly it is not normal for a car to periodically dump a lot of coolant, does anyone have any suggestions? Both he and I are not satisfied with the dealers forget-about-it-don't-worry answer. Thanks.

This happened only once, everything has checked out fine, he has used the car several times at operating temp and it has not happened again, right? I would not go crazy at this point. I'd take the dealers advice, and keep using the car. I would not advice prolonged idling, or even short idling over the winter. Either store it, or use it.

Car nose "in", ambient temperature in the "nose end" of the garage went up to?

Thanks for the info. Willwest are you suggesting that a temperature sensor got fooled causing the overflow? And this is because the front of the car was a different temperature than the back? Would you explain a little more.

willwest = willard (another computer) First, remember that the 996 has the A/C compressor enabled at all times unless you specifically turn it off. And, when mine is in the garage the sunroof is always tilted open, something I learned from my first Lexus so the moisture trapped on the A/C evaporator surfaces during the previous operations could escape during the night. In any case the automatic operation of the A/C would have added to the engine cooling burden of the radiators, more so if the windows are open, even slightly. Bad enough if the radiators were burdened with cooling the engine water jacket and the A/C refrigerant with the cabin closed, but with it open!!?? So with no exhaust fan to extract the air from the garage the atmosphere in the garage may have become "super-heated" (100F++ ??) during that 20-30 minutes. I have added a switch inside my glovebox that interrupts the A/C compressor clutch circuit so the A/C NEVER runs autmatically (nor beyond my control in defrost/defog/demist mode)during the wintertime months. When using the 996 A/C in the summertime if you do not remember to manually select airflow routing (which by default will deselect windshield surface cooling airflow, a real waste of cooling capacity and...) the system will chill the interior surface of the windshield and on a hot and humid day will result in condensation forming on the windshield exterior, sometimes so suddenly as to be hazardous.

I had a similar problem with my Boxster S belching coolant all over the garage floor. I had previously (in a boneheaded move) unscrewed the coolant cap, and somehow managed to throw off the pressure of the line. The car would just spew coolant all over the place. Maybe I improperly threaded the cap? Anyway, my dealer basically drained the entire coolant reservoir and refilled, reestablishing appropriate pressure. He said that these coolant lines are very sensitive. Now I just leave mine alone.

For almost any modern day vehicle the coolant system temperature will oftentimes climb above 212F (sea level atmospheric pressure boiling point), once the vehicle is shut down. Especially so if the vehicle has just been driven hard (It is a PORSCHE), and/or with the A/C operating on a hot day. pressurization raises the coolant system's boiling point above 212F. So if your coolant cap was not tightened enough to allow the system pressure to build and prevent boiling over....

You guys are great, thanks. Why couldn't the dealer give an answer similar to the ones you have posted?

Yeah, we know, but thanks anyway....