997.2 has dumped coolant - help!

[Dazzled]

I'm at the top of the Grimsel pass in Switzerland. Just stopped for a break after 100 mile run and the car had dumped a load of coolant from the overflow.
There was no sign of overheating before the engine was switched off. No warning lights or anything.
Any ideas as to why this might have happened? Possible combination of heat and altitude?
As a temporary measure I'll top it up with water until i can get it to a Porsche dealer to fill with the proper coolant.
Any ideas on why this might have happened?

[Polome]

This could be many things.1 ..is the under engine cover fan working ? 2 Check the radiator fans are working ( switch on engine & ac and you should hear fans in radiator pods running. ) p.s. This only checks that they do run not if the temp switch that controls them. If the temp gauge was showing normal and very hot engines & high ambientit may be No 1 at fault . Many other things but these are easy checks. Good luck. Ian

[EGTE]

Liquids bool more easily at lower atmospheric pressures.

Perhaps that's what's happened (and the overflow's done its job)?

[996TT02]

EGTE said:

Liquids bool more easily at lower atmospheric pressures.

Perhaps that's what's happened (and the overflow's done its job)?

The pressure in the system is determined by the cap, so that does not apply.

[996TT02]

Could be cap problems, could be previous overfilling, or is it below the recommended level now? Certainly spirited driving up a mountain will test all systems so any previously unnoticed faults will be brought to light.

[Dazzled]

Ok. So an update.
Thanks to all those who took the time to reply on here and especially to Mark Pearce at Stirlings who spoke to an OPC (Exeter?) on my behalf.
All suggested that the altitude and temperature had a part to play in it.
Having let it cool down I topped it up with 2.5 litres of filtered water. Ran it, checked it, ran it again and checked it again. Level remained constant as did temperature.
Normal service has been resumed.
The car has since done another 150 miles with no issue.
Thankfully the coolant is still predominantly pink but I'll take the precaution if getting the proper Porsche approved coolant on the next leg of the journey to Turin.
Odd thing to have happened and caused much interest in the car park of the Grimsel Hospiz. It was like touring with the Caterham all over again.

[Fish]

Had that happen in a heat wave up one of the passes in a TVR... stop have coffee, blag water refill continue!

[Heaveho]

Watched a 986 Boxster do something very similar at the top of Applecross a couple of years ago, but it's normally the cap on the early cars, a £9 upgrade to a later cap seemed a cheap fix! Glad it's ok.

[ScienceTeacher]

I had this exact problem with my 996 Carrera. I had slightly overfilled the tank and did exactly what you did is gave the car a work out the stopped. No cooling air passing over the rads, engine stopped in my case so no coolant circulation - heat sinks into coolant, cap pops open, pressure lowers, coolant boils, cap forced open as coolant ejects. I lost 3 litres in a dramatic fountain from the back. I guess that's why we have a pressure release cap so hoses don't pop off. I always carry 4 litres of DISTILLED water as I have had other leaks too. In the summer it is quite fine to put lots of this in ~5 litres or so. Regular water should ideally not be used as it contains some dissolved salts which will possibly precipitate put in the cooling system. Really you should drain and refil with the correct coolant, but this is probably unnecessary.
I have enjoyed this Swiss pass and others, I hope the dramatic problem has not put you off your stride.