Boxster Overheat and Coolant Waterfall
 

Hi Everyone!

I was driving to work the other day and the temperature gauge greatly rose followed by flashing on the dash. I pulled over to see what was going on and there was a waterfall of coolant on the rear passenger side right next to the tire. I popped the trunk, the cap nice and tight and unscrewed it. Steam started shooting out along with boiling hot coolant. Thinking it was the thermostat, I replaced that and changed out my coolant with 5 new gallons of Porsche coolant. I am still having the same problem.

Any other ideas?

I have two guesses: broken water pump or leaking coolant tank. Look under the rear trunk carpet to see if you find coolant. If so, suspect leaking tank. This may be a wrong conclusion, however, if the overheat caused coolant to overflow and saturated the carpets. Sounds like that didn't happen given the cap was dry when you first looked. Of course a broken hose or hose clamp could be the culprit, but a successful refill would argue against that. So I'm thinking water pump
.

Even though the water pump is not leaking, doesn't mean that it is still good. The vanes on the plastic impeller may have broken off. Ask me how I know this.

Spinnaker. I'm scared to ask LOL. And thanks so much guys. Just ordered a new pump hoping this is it. It was about time to swap it out anyways.

If the vanes on the pump have broken off, look for all the pieces. If you can't find them all, you might consider a reverse flush to see if you can get them out of the cooling system. Ingested pieces can block flow and lead to local hot spots. Good luck.

Overheating, no waterfall
 

So after swapping the thermostat and water pump and went on a decent 20 min drive. Temperatures were quite low but then shot up again. No coolant boiling/ waterfall this time however. On the old pump, there was one plastic piece that was broken off but Did not see in the bay. How might one do the reverse flush?

Once again I appreciate everyone's help!

Check the coolant tank for leaks. Pull up the carpeting in the trunk, if there is coolant there, most likely it's the tank.

Did you follow the procedure to properly get all the air out of the coolant system?

Car shops charge ~$90 to do this using their coolant vacuum systems to ensure no air bubbles.

Just filling it via the coolant fill tank cap will not do the trick and cause more overheating and premature water pump failure.

Also, you need to use distilled water with the coolant concentrate if doing it yourself and not using a premixed type.

For the cost of equipment to do the jobs right its best just to have the car shop do this for you in this case, unless you already have the proper equipment.

Update - Sounds like maybe there is a way to do it yourself without a vacuum system.
Pelican Technical Article: Boxster Coolant Replacement / Boxster Coolant Flush - 986 / 987

Check also the thread below, it seems this part is also a common culprit, i already know of three people excluding me that experienced this problem apart from people who posted here in the forum. The part is a total crap imo that's why its also a common source of coolant leak.

http://986forum.com/forums/general-discussions/47644-coolant-leak-valve-inside-engine-compartment.html