My car has started running hotter than usual a couple of times this past month, only on days when it was hot (95 - 100 degrees outside). The first time I noticed it was doing city driving when it was 100 degrees outside, once I was on the freeway it was fine until I got up to about 85 or 90mph, then the temperature gauge started rising rapidly (this is up a fairly steep incline though, the 2 North in Los Angeles). Obviously I just slowed down to 80mph and everything was fine. Since then I've had that happen a couple of times, but I'm always careful to just slow down and not let the car get too hot.

My typical engine coolant temperature is 200 degrees F, the last time my car got to hot I plugged in my obdii reader when I got home and the ECT was 240 degrees F.

I'm guessing the problem is my thermostat or air in the cooling system so I'm going to try those fixes soon, but one odd thing I've noticed is when I turn my car off the radiator fans don't run at all - is this normal for Zs? I would assume not, since I've noticed that if the car is fully warmed up and it's hot outside, if I turn the car off to go inside a store for a couple minutes when I start my car the temperature gauge starts off pretty high, then drops rapidly. I'm guessing this is because the cooling system should be running for a bit when I first turn the car off, but what would cause it to fail like that?

 

Nothing works when the car is off! Thermostat, plugged up hose, or air in the system