Normal Operating Temp ????

[j.fro]

Here's my experience on the same question; looking forward to input. I've got the Dash Command app and the elm wifi transmitter. In my 1999 996 C4 on 95+ degree days I'll see coolant temps stabilize around 216 running 71 on the highway. In highway traffic accelerating/decelerating, temps get to 221, but no higher. On cooler days, temps never get that high.
How hot is too hot?? 225? 235? 245? 250?
FWIW, my 986S with center radiator and hood vents never gets over 219, and cools down to 180 quickly once we're moving.

[JFP in PA]

Originally Posted by j.fro

Here's my experience on the same question; looking forward to input. I've got the Dash Command app and the elm wifi transmitter. In my 1999 996 C4 on 95+ degree days I'll see coolant temps stabilize around 216 running 71 on the highway. In highway traffic accelerating/decelerating, temps get to 221, but no higher. On cooler days, temps never get that high.
How hot is too hot?? 225? 235? 245? 250?
FWIW, my 986S with center radiator and hood vents never gets over 219, and cools down to 180 quickly once we're moving.

OK, here's the problem: When the overall temp is 216F, there are parts of the engine that are hotter, and some that are cooler. That differential is not particularly good for an alloy cased engine, and the thermal loading contributes to things like cylinder head cracking.

Secondly, if the coolant is at 216F, the oil is probably near 230F, which both shortens its life expectancy as well as reduces its ability to cool the bearing surfaces (one of the principal functions of oil).

[j.fro]

So 216 is not good. Any thoughts on the solution? Do I need to add a center radiator to the car? The car has 88k miles and I believe the water pump is original (and coolant). Is this a sign the impeller is going?
If this is dangerously hot, any thoughts on why Porsche didn't put the center radiator in all cars? Or why the idiot light doesn't come on until much hotter (250)??
FWIW, in my 986 which runs much cooler, I did an old V8 hot-rod trick: I drilled a 1/8" hole in the T-stat plate so that there is always some coolant flowing. I know the Porsche system already has a bypass in the heater system, but it seems to be part of the difference.

[jmatta]

This is why you install the LN low temp thermostat, just like Porsche's high performance engines...opens much sooner and stays open to allow coolant flow. Anything to get the temps of both coolant and oil down is good for the engine.

[JFP in PA]

Originally Posted by j.fro

So 216 is not good. Any thoughts on the solution? Do I need to add a center radiator to the car? The car has 88k miles and I believe the water pump is original (and coolant). Is this a sign the impeller is going?
If this is dangerously hot, any thoughts on why Porsche didn't put the center radiator in all cars? Or why the idiot light doesn't come on until much hotter (250)??
FWIW, in my 986 which runs much cooler, I did an old V8 hot-rod trick: I drilled a 1/8" hole in the T-stat plate so that there is always some coolant flowing. I know the Porsche system already has a bypass in the heater system, but it seems to be part of the difference.

Adding the center radiator will give you higher heat transfer capacity, which will change the rate at which the engine sheds heat, but not its steady state temperature. That is controlled by the thermostat.

[mikesz]

My 99 tended to run hotter than I like. A few weeks ago I replaced the thermostat, water pump, and front engine mount. I had the time and do most of the work myself. Car has 80k on it and in a little over a year I have experienced most of the Boxster GREMLINS! So with that said I took the old thermostat and immersed it in boiling water to see if it opened properly. It opened but not all the way and when I let it cool did not close all the way indicating to me it was not working properly. Since doing the work my temp gauge is much more consistent. I also replaced the engine bay fan. it was binding and blowing fuses. Had the same issue with the 2 front coolant fans. I am glad I changed out my thermostat just for piece of mind and the work wasn't all that difficult. You may want to make sure all the coolant fans are working properly also.