The system pressurises itself when hot.

Hence the instruction not to remove the filler cap when the engine is hot.

 

The cooling system on them is a bit of a logistic nightmare and has metres and metres of tubing. My 4S had all the radiators replaced and then all the tubing. After the problem did still not go away it transpired that the fault was a 64p seal. The warranty bill ran to thousands, parts alone were into 4 figures.

Porsche are pretty good with this sort of thing. I wouldn't worry unnecessarily. Pressure test will point them in the right direction.

PS: Should have bought a 2S

 

Mole, look up Boyle's law. All it really means is the cap on the radiator is in a separate bottle at the top of the engine bay, not on one of the radiators. That would be hard to reach and all the coolant would fall out if you removed it. The Hondas have a radiator cap and a catch tank for any expansion overflow, except the NSX wich is like your car.

Not to be confused with Coles' law. BTW. That's chopped cabbage and mayonnaise.

As lee say, the waterways (and oilways) on F6s with front triple rads and oil coolers are a f ucking Freudian nightmare. The chances are it's something really stupid.

 

That extra 44mm matters and anyone who tells you otherwise is in denial.
Thanks for all the responses, gives me a bit better understanding.

 

That's exactly why I bought my 4S too.

 

BTW, the system is pressurised to prevent the coolant from boiling so quickly, encouraging more effective cooling. This is why Spoon/Mugen rad caps have a higher pressure rating. They keep the coolant at a lower temp because they pressurise the system more.

A pressure test will help to find any leaks.

A sniffer test can rule out/confirm a dodgy head gasket by finding out if there are exhaust gases (sulphur dioxide) in the coolant.

An expansion vessel should only be topped up to the 'minimum' mark. If it is filled higher than that, fluid will be expelled from the vessel when the coolant heats up and expands.