Mine does this also at high RPM or going up hill the mountains. As soon as get level or down hill it comes back down to 80*. I thought it was normal as it never really reaches the 90* mark and come down when I get out of the pedal.

 

Yeap this is strange...still haven't figured out what is causing this and as mentioned before there are numerous threads on the net..but nobody has come with a permanent fix or a solution to this...so my question is....all those infected by this problem do you just live with it or ???

Thanks

 

I just keep an eye on the temp when I run it hard or I'm going up the mountain. It mostly only hapends when I'm north of 3k going slow, once I start moving it drops.

 

Did you ever replace the thermostat? Technicly the t_stat is not supposed to be fully open until like 210. The thermostat works on a curve. Just because it opens all the way and the temp comes down does not mean that the opening curve is correct. When I got my 04 CTT it stayed rock steady at the 180 mark and never went over. After about 3 years I had the same symptoms as you. The Cayenne has an awesome cooling system and even in 115 degree las vegas heat I never had a problem.

 

where do you saw hot? its normal temperatures.

 

Mr. Haney...did you replace the thermostat after having the high temp symptom? Was it the cure?

 

I never did replace the thermostat, lost an ex. valve first. But now that I have the old one out I'l probably throw it in a pot of water and test against the new one just to see. As my mileage got higher it also seemed like the duration and frequency of the fans running after shut off was snot the same or the same. There is a motor control unit for the fans on the back of the radiator shroud at two o'clock to the small fan. I think it's a progressive type controller where it hits soft at startup and ramps up to the variable speed.

Looking at the service manual, When you look in the Porsche parts diagrams it doesn't have any listing for a control unit there, in electrical or in cooling. I'm guessing that the control unit comes with the small fan which is for the ac. Since the control unit is not listed in the listing of Control units for the vehicle, it probably doesn't have to be coded.

From the Cayenne aftersales training pdf-

The thermostat starts to open at 181° F (83° C), lift is 9.8
mm at 208° F (98° C), and it reaches its maximum
opening at 221 F (105
° C). Coolant temperature is
measured at the engine block inlet. With the thermostat
open (full circulation), the coolant is brought by way of the
radiator at the fr
ont of the vehicle back to the intake side
of the water pump.