dnorm333

I have a 2003 Boxster S and noticed about of cup of what I thought was coolant under car about week ago. As is winter I rarely drive but start up once a week. Have had some below freezing temps about a week prior to noticing the small amount of liquid, assumed coolant, under car near right rear wheel. A week later I drove car about 40 miles with no issues. Later that day on trip back, about 30 minutes in, the temp light started flashing and car temp came up, back down, and then back up again. The temp needle would bounce back and forth between normal temp and hot. Light would be off and on and finally red lined as hot and stayed. Pulled over about 15 minutes shut engine off, cooled off a bit, and got car home with no issues. Once home, I looked at coolant level. Reservoir was empty and cap warm with some steam residue present on inside trunk latch. A couple days later, I filled reservoir and looked for any leaks under car but were none. I drove it up street for about 10 minutes and voila, red temp light flashes again. I get car home and reservoir tank is empty but no signs that it had leaked under car. Checked under trunk carpeting and does seem to be wet from reservoir leak. Checked oil to see if maybe gasket bad as heard coolant would seep into engine and diminish oil viscosity and raise level on dip stick. It seems fine. Exhaustis fine upon start up. Any ideas? Plan on flat bedding to local porsche dealer before temps hit freezing again this week. I appreciate any feedback.

Macster

Get car flat bedded to dealer and have what appears to be -- based on your posted info -- a failed coolant reservior tank. If coolant cap not newest part number I'd replace that while you are thinking about it.

Symptoms due to loss of pressure, loss of coolant and continued driving. If coolant loss substantial just dumping in some water or anti-freeze and water ain't going to refill the cooling system completely.

While the tank level may register "full" when you start engine and get engine warm thermostat will willl open and allow coolant from tank to enter cooling system proper. Tank level will of course drop and probably no coolant will be visible in the level sight window.

That the system still has a substantial leak means the fluid you added could be forced out again so system is still way under filled with coolant.

Proper refilling a Boxster cooling system with fresh coolant is not straightforward without proper equipment. Dealer service has this equipment though and after identifying source of leak, the coolant tank or perhaps a failed hose or even a water pump and addressing the source will then refill the cooling system with the proper mix of antifreeze and water and in such a way no air pockets remain.

Sincerely,

Macster.

Sputter

Best guess is a bad coolant tank (assuming you're correct in that it's not in the oil). Possibly a bad coolant cap but you're losing way too much coolant in such a short period of time.

Driving it in that state isn't the best plan.

dnorm333

Thanks for the input. I have a flatbed set up for tomorrow and plan to take to Porsche dealer in AM. Will admit I was bit worried at first but hopefully is a minor fix. I feel better after oil looks OK upon checking. One hears "worse case" scnarios when looking at these things online and always feel good about input on Rennliist with actual Porsche owners. Thanks for the input and will post update once it sees dealer.

dnorm333

Update - Had a bad thermostat. Was tapping on too early. First thought I may have a combustion into coolant system issue and very glad disgnostics showed all OK. Water pump was getting bad as well so replaced it while I was at is and got oil change with new magnetic oil plug. Just under $1k but coulda been worse