2002 Boxster coolant mystery...
 

I have a 2002 Boxster (non-S) and I have something of a mystery on my hands with the coolant system (I think).

Had it out for a drive, and stopped for a beverage. I was away from the car for maybe 3-5 minutes. And while driving, I don't think the red indicator light was blinking. When I came back out to the parking lot, there was a large puddle of coolant on the ground. I don't know if it had been leaking while driving up to the moment I parked it or not. Drove it 2-3 more blocks, then called for a tow. Another large puddle appeared while waiting.

When I got it home, I filled up with more coolant and distilled water, started it up and waited for it to get to normal operating temperature. I was watching for leaks the whole time while waiting, but none appeared. The temperature went up a bit more, then the red warning light started blinking. I shut it down, but I still never saw a leak. I know that the expansion tanks on these cars is known to get old and crack, but that does not seem to be the case, since I did not see any leaks.

Any guesses about what was happening?

Thanks in advance. You guys have saved me thousands of $$$ over the years.

Water pump not circulating. Bubbles over.

Thermostat stuck closed.

Res tank crack, carpet wet in trunk.

Bad radiator cap (not on the radiator of course)

I appreciate both responses. Thank you guys. I will check these things out. I am particularly suspicious of the radiator cap, since I think it is an older one, and I noticed some small white crystals left over from evaporated coolant.

I wouldn't rule the expansion tank out entirely - when mine went it didn't dump until I had shut the car down. Didn't see/hear anything until I turned it off in my garage and heard the car start peeing. No drips on my driveway or street.
Just something to keep in the back of your mind.

Good luck!

ours was the thermo stat. same symptoms

I am gonna go with water pump/thermo. I went through a bad water pump a couple years ago and a leaking expend tank just last month and it looks like the first problem more than the second. However, it is super easy to pull up the carpet and board just to check, not to mention just buying a new cap and screwing it on. I am assuming you are on the wrong side of PA, but if you are near me, I am willing to help.