MY 03 PORSCHE BOXSTER OVERHEATS AND LOSES COOLANT, WHAT IS WRONG WITH IT?

Change the cap to a new one and see if that's the problem.

First I would try what joemom recommend and if that does not work I am going to recommend something you may or may not want to try but it worked for me. Lucas Radiator And Block sealer. No promises but it has been working for me for a year now and still no leak. By all means this is not a permanent fix but may hold you over long enough to save the funds to do it right. One more thing if it does not work the first time do not continue to add more hoping it will work it will cause more problems like clogging up your cooling system. If you do decide to try it hope it works for you like it did for me.

It could be your overflow tank it seems to be a weak point in the Boxster cooling system. Heres a video that shows how to test and find the leaks: https://www.youtube.com/watch?v=5WrgWIVFnpw

Heres a link to the OE replament part if that turns out to be the problem. http://www.partsgeek.com/gbproducts/WC/131-01136567.html?utm_content=YN&utm_term=1997-2006+Porsche+Boxster+Expansion+Tank+Original+Equipment+W0133-1647661+97-06+Porsche+Expansion+Tank+2004+2005&fp=pp&gbm=a&utm_source=google&utm_medium=ff&utm_campaign=PartsGeek+Google+Base&gclid=CLmmnsq4pMYCFdcZgQodVIANlQ

Check your hoses and clamps running to the pipes going to the front of the car. On shut down, the engine heat soaks, and raises the pressure enough to cause a leak. The water pump is also a suspect, but it's easy to change. Good luck!

Left carpet in trunk and check if there is coolant. If "yes" you need to change out the coolant tank - a bad design, make sure you have the tank pressurized after refilling coolant.

Hello all, i know this issue is well past done but to any readers having a similar issue; My boxster s 02 one day dumped its coolant? was running fine had good coolant level then i suddenly found myself stranded, apon inspection i found no leaks only some coolant residue near the coolant tank, i would add coolant and distilled water and it would run fine for a short while but soon loose coolant, To remedy this problem i removed the plastic cover (which is located on top of the coolant reservoir along with the dipstick and oil fill cap) that hides the bleeder, valve for the coolant system. I then opened the bleeder by placing it in the up position (which literally means positioning the metal tab up so it pointing to the sky) turned on the heater to full blast,(after making sure the dipstick and oil fill cap were secured lol) ran the car for about 15 minutes filling with coolant and water as needed, when it remained full i closed the cap for the coolant but left the bleeder open, drove around and replaced liquids as needed, that seemed to fix the issue, seems air or something got trapped in the system.

I have similar problem. With my bokster 2011.. did the same .. altho the coolant valve was in the engine area not from the back ... it stil need more and more coolant in a short time... with overheating alarm ... Wt I can do