My car recently overheated and the radiator cracked, which I had replaced along with the thermostat. Since then, it still overheats on very hot days (Arizona) which I mitigate by turning off the AC. It runs fine in the morning when its 90 something degrees, but when it gets up around 105 or hotter inthe afternoon, the gauge starts creeping toward the red line. I've had it into the dealer a few times for the problem, but they can't figure it out. I'm wondering if the water pump may be under-performing. Any ideas?

My car recently overheated and the radiator cracked, which I had replaced along with the thermostat. Since then, it still overheats on very hot days (Arizona) which I mitigate by turning off the AC. It runs fine in the morning when its 90 something degrees, but when it gets up around 105 or hotter inthe afternoon, the gauge starts creeping toward the red line. I've had it into the dealer a few times for the problem, but they can't figure it out. I'm wondering if the water pump may be under-performing. Any ideas?

-Does the fan come on? (If not its a sensor).
-You might need a different thermostate that is for very hot environments.
-I think you can buy add on parts from aftermarket store that cools the oil and/or the radiator fluid better than the original equipment.

-Does the fan come on? (If not its a sensor).
-You might need a different thermostate that is for very hot environments.
-I think you can buy add on parts from aftermarket store that cools the oil and/or the radiator fluid better than the original equipment.

Yeah, I've observed both fans operating. The confusing thing is it overheats while moving at normal freeway speeds. I've operated the car in this environment for 5 years, never had the o/h problem until this summer. I think it is unlikely that the new thermostat is bad, and it doesn't seem like the symptoms of a thermostat problem. Thanks for your consideration.