Benton, welcome to the addiction! Sorry to hear of your troubles. You came to the right place. I had to read your post a couple times to get a clearer picture of what is going on. It sounds like the car operates relatively normally until a large load is placed on the engine. I take it replacing the thermostat changed nothing.
Just to eliminate the obvious have you looked in the air intake area ahead of the radiator stack to see of there are any obstructions like leaves or a plastic bag? These cars act like vacuum cleaners and suck up all kinds of crap.
Next, it would be good to get more accurate temperature readings, the dash gage is not reliable. Do you know how to get temperature reading on the AC display?
1. Push and hold up and down (each side of Fan Control button) until you get zeros in display on left.
2. Then push up button to right until you get to 16 in the display.
3. Then push center fan button to read digital coolant temperature in degrees C continually in the display until you hit the temperature button. The car can be driven in this mode to get ongoing temp readings.
80 C is 176 F
85 C is 185 F
90 C is 194 F
95 C is 203 F
100 C is 212 F
105 C is 221 F
110 C is 230 F
115 C is 239 F
120 C is 248 F
125 C is 257 F
130 C is 266 F
Since the issue, if I read this correctly, is only under load I would suspect the radiator first. Also check the spark plugs to see if there is any sign of a head gasket issue (while unlikely) just to be certain.
H
