I'm adding an aftermarket water temp gauge. What is the nominal temp that our cars should running at, and at what point do I become worried. I lost my last engine to overheating and cracked the front plate.

Just in case it makes a difference, im running a JDM S5 motor.

 

The temp guage should read VERY close to the T-stat's rating. Get a mazda T-stat and I belive the temp is 190 but I am not positive. The temp might creep up with AC but anything OVER 215 is too hot IMO. Also try water wetter additive. My 7's temp moved alittle until I added the stuff now it is rock solid, and helps alot with crorsion protection of the alluminum!!! get it @ autozone or Napa.

 

My mantra for today:

"Clean the leaves out from around your oil cooler."