So I have been dealing with this for some time now and its getting old, my 96 montero wont stay cool when its hot outside. Let me start with what I have done and what the symptoms are. I have replaced
2. Fan clutch
3. A/C fan
4. Coolant flush
When it is 85 degrees or below I have no problem, I can run the AC or do anything and it stays nice and cool. With it is hotter outside I can run the AC and it will stay cool for awhile but then after 20 minutes or normal driving the temp starts to go up and when I stop it goes up fast. It has never overheated or spilled coolant so my first thought was maybe a bad temp sensor on the thermostat housing but that doesn't seem to fit to me, it works when it is cold outside so i'm not sure. When the car does start to get warm and I turn the AC off the temp gauge instantly drops 20% or so and then slowly cools down from there. A friend of mine thought because of the instant drop in temp when i shut off the AC that maybe I have a bad ground wire from the engine to the frame or for the accessories a bad ground to the body. There are only a few more parts I can replace like the radiator and water pump but i'm not sure if that is necessary. Any suggestions on this would be amazing, thanks guys!