Overheating problem
 

My 97 F-150, v-6, overheats in the summer. Without the AC, the gauge shows about 190 degrees. Turn on the AC and the temp quickly starts to increase to at least 210 degrees. Probably would go higher but I turn it off at 210. This is a summer problem only, it runs about 160-170 in cooler weather when the AC is not needed.
The thermostat has been changed, the coolant has been changed, the fan works. What could cause the AC to increase the engine temperature so much?

Thanks.

It sure sounds like your radiator is plugged externally and not letting air thru the coil, or internally and stopping heat transfer fromt he water to the tubes. Wash the outside of the radiator with a garden hose and make sure you can see light thru the coils. If it is clean, you probably need a radiator boil out. With a 15 year old truck , i would buy a new radiator and be donw with it.

If the V6 is anything like the modulars your only issue is it is running too cold, 210 is the optimal temperature and they run up to 230 under heavy use in heat. 160-170 is way too cold. Should be either side of 200 under normal conditions.

I agree 210 is great!

Just a few suggestions. If you live in a salt region check to see if there's any fins left between the rad coolant tubes. I had a 92 Lincoln once that was missing 40% of the fins when I pulled it for a leak. You should also be running 50/50 mix antifreeze good to -35F. If the antifreeze is too pure it won't transfer heat well.

Overheating problem
 

Thanks for your reply. Frankly, this is the first time I have heard that a Ford can take prolonged operation at 210 degrees or higher--and I have asked a lot of car people. Can anyone quote a source saying what the design temperature is for this V6 engine?

More to the point of my "problem", can anyone tell me why just turning on the AC in the summer will cause the engine temp to rise by 15 or more degrees in normal highway driving (not sitting in traffic or pulling a heavy load)?

Thanks again.

Your thermostat rating should be between 188f to 195f when it starts to open and fully open between 208f and 215f, when your truck is cold start it up and put you hand on the top radiator hose, the hose should get hot (188+) quickly, (a few seconds) when the thermostat opens, if it does internally it should be working like it’s intended to, externally any coating of most anything on the radiator will not dissipate the heat like it should, it’s like rapping a blanket around your self.
When you turn on the AC it turns on the compressor and that is adding load to the engine, if it’s not cooling correctly the temp will rise.