I have a 93 Lexus ES300 with 174 K on it. I think I have the highest mileage on this board :D
Anyway, I drive 80-90 miles to work and back everyday. In cold weather, under 60 degrees, the car does not overheat. However, recently due to the incoming summer and 65 -75 degree weather, I have noticed that after about 30 minutes/35 miles of driving the thermostat starts rising from the middle mark. Once the thermostat starts rising, it pretty much rises all the way to the top quickly unless I slow down and turn the heat and fan on at full blast.
I first noticed this after I had a transmission replacement at 162K. I also replaced the seal between the transmission and the engine.
I had a dealer check it a while back for $100 (ugh) but unfortunately we had a few cool days and they could not replicate the problem. At that time, I had not noticed the warm weather effect.
Any ideas on where to start to fix this? Thanks
Colloe3