[MNBoxster]

Hi,

First, lacking a very graduated Temp Gauge, the display is somewhat inaccurate. You have hash marks at 180°, 200°, and 250° so you can only estimate the temp if the needle is between these marks.

Second, the temp will swing depending upon speed, load (the types of things you describe in your post).

Start the car, turn the AC ON and get out, walk to the front and get down on each side to be sure you hear both cooling fans operating (they default to ON with the AC on). Turn AC OFF and allow the car to exceed 185° (the threshold for energizing the cooling fans) and get out and listen again. This will eliminate the temperature sensor as a possible culprit.

Check to see that the coolant level is good. That the system is properly bled (there's a Bleeder Valve located under the escutcheon (Black Disc) under the Coolant Cap, Oil Filler Cap and, on your car, Dipstick). Remove the caps and dipstick and carefully pry up the escutcheon. Under it you'll see a Bleeder Valve. Lift the metal ring, replace the caps and dipstick, and start the car and allow it to fully warm., Then rev the engine to say 2500 several times (this will allow any air in the system to bleed off). Close the Valve (careful it will be hot - take necessary precautions), Shut the car down, and after it cools, replace the escutcheon and caps and check the fluid level, top up as necessary.

Now, you may need to clean out each radiator. These accumulate all sorts of debris from leaves, cigarette butts, insects and even birds. As this debris gets sucked between the radiator vanes, it reduces the cooling area of the radiator(s). It's best to raise the wheel on a side, remove the ducting and back-flush the radiator with a Garden Hose to flush the debris out the same direction it went in. If this has never been done on your car, expect to see an almost unbelievable amount of debris expelled. Hope this helps...

Happy Motoring!... Jim'99