Vonhendon said:
Envoy run's one tick below 210 deg. when AC isn't on but once it's on it goes up 3 tick's above 210 deg. before I started having problem's last summer it always stayed at 210deg. Had a shop look at it more then once last year and they changed my T Stat to one that I didn't want. They said it could be my Rad. but my question is I don't have a prob. until the AC is on. At highway speed's it does come down a little but in traffic I get very nerve's so I plan on changing the Rad.
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A few years ago, my Lexus was doing something similar. I noticed one day coming home from work, on a pretty hot summer day, the temperature needle was approaching the red. Since I was on an expressway where I couldn't pull off/over, I quickly turned off the a/c and turned the heater on high. Drove her home that way.
I screwed around with that car until summer was over--meaning, I flushed the radiator, changed the radiator cap, replaced the thermostat, etc. No change.
I later decided to remove the fan shroud, and open up the front grill. Then, I took an air gun and thoroughly blew out the condenser coil and radiator. Put everything back together, and ran the car under the conditions that was causing it to overheat (not literally). Nothing. In fact, the car never ran cooler. And, I never had another temperature problem again.
I know the Envoy and Lexus are so dissimilar, it's like comparing apples to oranges. Nevertheless, I thought I'd share my experience anyway.