Boosttt,

I had this same issue with my 2001. I did a lot of research on fixes. First, all gauges are going to read slightly different. They are not ultra calibrated. My 2001 runs dead center of the 0 on the 180. If I drive hard or pull a long hill, it will move over to the dash or get to 210. But, on the downhill side or at normal cruising it NOW cools much quicker. 99 C 2 has great ideas to check your fans/relays, but in the cooler part of the day driving at high enough speeds, you should not need your fans to cool.

This is what I did:
1. I pulled my front bumper and thoroughly cleaned the radiators. You cannot just spray them out....they get too clogged up with debris and it gets stuck. You need to brush them out extra well forcing all that crapped to dislodge from the fins...and believe me, it is in there.
2. During a big service I installed an LN Engineering 160 T stat and a new water pump.
3. I added TWO bottles of Red Line Water Wetter. The bottle says good for 3 to 5 gallons. In the 996, we are at 6 gallons. So, I figured two bottles was the right concentration for the prescribed 3 gallon directions. Being in AZ, you should consider doing 2 bottles and running 70% distilled water and 30% Porsche coolant. You rarely see a freeze and the cooling is much better with more water.

The results of my efforts: With the lower T stat, on cooler mornings I'm at the left side of the 1. But, when it heats up, a fully open T stat is fully open and I'm back in the middle of the zero. The cleaning has allowed it too stay cooler longer and cool quicker when the fans go on or I'm cruising without pushing it at normal speeds / 80mpg or so. My fans rarely go on as I'm not in stop and go very much, but when they do cycle on, it cools noticeably quicker.

Keep us posted on your results. Good luck!

 

You need to run 2 bottles as our system requires a lot more coolant. Worked for me.

 

Added more distilled water, and 2 water wetters. The needle stopped at the 0 of the 180 and never moved over. It dropped a bit more here and there. Driving in 103 degrees today. Thanks for the advice!!