[Michael1]

Have you removed the radiator cap (WHEN COLD!), to be sure the coolant level is all the way to the top. Also, is your coolant reservoir full. After the system gets hot, be sure the coolant reservoir is topped off, so that when it cools, and draws in coolant, the reservoir doesn't become empty and just draw in air.

It could also be that you have a defective radiator with blocked tubes, or there was material left over from manufacturing that has blocked some of the tubes. After running the engine, turn it off (remove the keys so someone doesn't accidentely start it), place your hand in between the fan blades, and feel the radiator fins for uniform temperature. It should be very hot and uniformily hot, so be careful not to burn yourself. If there are cool bands, the tubes are blocked.

In cool weather, does the temperature stabilize? If so, then it also could be a thermostat that works, except not opening all the way. If you see wide changes on coolant temperature, near "C" when going down hill, and near "H" when going up, your thermostat may be stuck partially open.

I have noticed that the H3 does run hot in slow traffic on hot days. It never quite overheats, though, and the temperature comes down quickly when the engine speed comes up (increases fan speed).

Michael