Normal? Or a leak?
 

Had good run in my 986 today. When I left it sitting long enough to open garage doors, about two minutes, The cooling fans came on and it started to leak coolant just forward of the rear wheel. (Drivers side UK).
It slowed to a tiny drip when I turned off the engine.
Excuse my lack of knowledge but is this some kind of emergency pressure relief, or do I have a coolant leak?

It could be either, since the coolant overflow line AND a leaking coolant tank ultimately drip in about the same area.

Lift up the carpet in the trunk and look for wetness on the bottom of the coolant tank. If there is nothing obvious there, take the oil, coolant cap and oil dipstick out and remove the coolant tank plastic cover and have a look to see if there is visibly any coolant overrun around the cap and into the overflow hole.

If it the leak was on your passenger side I would say it was the water pump. I think it is the coolant tank.

Thanks
 

I'm no mechanic, so have arranged to drop car in to Local performance specialist on Monday. Have other issues, creaking front end and dodgy exhaust system bolts. Corroded due to ****************ty weather in UK :)
Will advise what problem was as it may be of assistance to others.
Only know about exhaust bolts cos it was up on ramp for service. Boxster isn't an easy car for an ametuer, not like you can lift bonnet and take a look!

make sure your over flow tank cap is screwed on completely and not cross threaded.