My "new" 987.2 w/ TPC turbo has been overheating on the track so I've tried some experiments to try to figure out what's wrong.Took a short city drive w/ ambient 89* and when I got home water temp was around 190. I sat in my driveway for about 10-15 mins.w/ the A/C on at 1500 rpm. Water temp reached 232* and rising so I quit. Dash "gauge" had barely moved. Is this normal cooling system behavior? I'm wondering about the thermostat being at least partially stuck closed. There was never a point where the temp dropped, like when the thermostat should have fully opened. It has a center radiator but it is dedicated to the intercooler.

 

My experience with my stock 2002 Boxster is under high ambient temperature conditions -- 116F -- the coolant temperature reached 226F but went no higher. I do not know what the in dash temperature gauge "read". It might have had the needle quite a ways to the right of "normal".

When I got home I talked to the service manager at the dealer about my experience. He passed my "data" and my questions to the factory. Factory replied with paraphrasing no warning light/no warning message about too high coolant temperature no problem. Essentially the in dash temperature gauge is just for "show". I used it to know if the engine was cold, warm or hot. Beyond that...

At another time I tried to get the coolant temperature to go higher and was unsuccessful. 226F is as high as it went.

That you observed the temperature climb to 232F and was rising sure doesn't sound "good". Were both radiator fans running? Were both on high? With my Boxster the fans came at low speed at 212F and switched to high speed at 216F. In both cases the fans turned off at 205F.

Several more things... Boxster radiator would not run at low speed. Turned out to be a failed ballast resister -- part of the radiator fan motor wiring harness. The fan would work at high speed. But I had the wiring harness replaced so the fan operated correctly.

In another case with my 996 Turbo I found one radiator fan not blowing air. Sounded like it was running though. I was in Fresno and the ambient temperature was nearer 99F than 89F but the engine coolant temperature was just fine. A/C was working just fine even with the car stationary and the engine at idle. With one fan out decided to turn back rather than venture out over the desert southwest into I'm sure triple digit temperatures. At the dealer tech found the radiator fan motor shaft had snapped. Motor was running but of course not spinning the radiator fan.

With this car another time for some reason I checked to see if both radiator fans were working. They were but the driver side fan was not blowing nearly as much air as the passenger side fan. At the dealer tech checked and reported no fan stage errors but the driver side fan was drawing a lot more current than the passenger side fan. I had him replace the fan motor.

More recently with my Dodge Hellcat I have observed the coolant temperature get rather high. Don't think I have ever seen it get to 232F. (Oil temperature I think at least one time got to 230F. This after some amount of time of town driving on a warm day.) But I have not tried to see how high the temperature can go before the cooling system's capacity then takes over and at least keeps the coolant temperature from running away and going too high.

In the case of your car the T-stat was fully open at a much lower temperature than 232F. I do not know the coolant temperature characteristics of the newer model Boxsters. They could be different and have a higher maximum coolant temperature limit before the cooling system reaches a point at which the coolant temperature goes no higher. To know this without potentially risky testing on your part I'd suggest you speak to a Porsche tech at the dealer. The ones at my local dealer were very good answering my questions albeit I never went back to ask a question without first getting permission from the service manager.

And as I touched upon above, you want to be sure both radiator fans operate properly. That they have a working low speed and a working high speed.

Have you checked the radiator ducts for trash? My Boxster's radiator ducts collected lots of mostly plant trash. I occasionally cleaned these out but no so much for concern about the trash affecting cooling -- I saw no signs of this -- but from the risk of corrosion damage to the A/C condenser and the radiator. But the newer model cars might have some sensitivity to radiator duct trash presence that might -- if bad enough -- affect cooling. (Word I have is these cars can run just fine even in high ambient temperature conditions with just one radiator and radiator fan motor.)

 

Thank you for taking the time to provide all that good info. My car is a Gen. 2 Cayman S but I don't know if he cooling system is materially different than the 986 Boxster. The dash "gauge" is indeed an idiot light tarted up by Porsche to resemble a real gauge. Geez. I am taking temps w/ my Cobb Accessport via OBD2.

I spoke yesterday w/ the mechanic I use and he also asked about the fans. I'm embarrassed to say that I did not check them but will today. And I don't know if the fans are even effective on the track unless perhaps they aid flow by creating negative pressure behind the radiators.

"In the case of your car the T-stat was fully open at a much lower temperature than 232F." Are you telling me that, based on the symptoms I have described, you think the thermostat was open or should have been open? The latter is certainly true but I have doubts about the former. From what I've read, the t'stat begins to open around 180 and is fully open around 210. I would think that if it fully opened I would have seen the temp drop or at least temporarily stabilize by 210.

After I first noticed the high temp at Road Atlanta I removed the nose, cleaned the center radiator and A/C condensers, and painstakingly tried to open up as many of the bent fins as possible. I also added screening over them, although that will reduce flow somewhat. This is a track/street car BTW.

 

Yes, the radiator fans come on w/ the A/C. W/ A/C off the radiator and engine bay fans come on around 207*.Unless someene has a better suggestion, I'm going to replace the t'stat and water pump and go from there.

 

I had nearly identical symptoms on my Ferrari 360 Modena , a mid engine car with two front mounted radiators, each with an individual fan. These fans are not needed at speed, but are quite important to promote airflow through the radiators when stationary or moving at slow speeds. One of my fans malfunctioned and once I repaired the wiring, the overheating went away.
I'd definitely confirm that your fans work properly before taking a peek at the thermostat.

 

FWIW I replaced the t'stat and water pump and it made no difference. I'm wondering about having the dealer vacuum "bleed" the system.

 

There are a lot of vaccum fill pumps (like airlift kit) available for cheap on amazon and they work well. Does the 987.2 have a bleed valve on the coolant expansion tank like the 986 does? Sometimes if you run around with that open for a week the air will work its way out. Be careful though, aluminum blocks don't take kindly to above-boiling temps.

 

LN Engineering recommends the Bilt deep oil sump and CSF radiators. I have a friend w/ a Raby 3.8 in his 987.1 who swapped his radiators for the CSFs and he said it made little or no difference. Anyone have experience w/ deep sumps?