Mitsubishi Repair: 2000 Eclipse overheats at low speed, mitsubishi eclipse gs, red line water wetter

Question
I have a 2000 Mitsubishi Eclipse GS Sportronic transmission. My temperature gauge goes up about a quarter inch while driving in heavy traffic (stop and go). If I turn the heat on for two minutes or so, it goes back down to normal. I've REPLACED everything (Radiator, Thermostat, Cap, Fluid and Water Pump). There is no fluid loss at all. The fan seems to be working fine. By the way, it only does this during the summer months (Phoenix, AZ). Please advise!!

Answer
Rodney,
Since the average temps in Phoenix between May-Oct. is around 100 F, it's not uncommon for the temperature gauge to read higher than normal.  Especially when moving at slower speeds with minimal air passing over the radiator.  It's possible there's a blockage somewhere in the cooling system, which is preventing proper circulation of your coolant.  Blockages can because caused by corrosion in the pipes, gummed up coolant, or various debris that may have entered the cooling system.  Also, lack of the proper viscosity engine oil will also cause your engine to run hotter than normal.  Make sure your using the proper amount of oil and the proper oil viscosity.

One thing you can try is to drain the system and add a higher water content ratio of water to anti-freeze.  A 70% water to 30% anti-freeze will help keep the temperature lower.  To that, you can also add a bottle of Red Line Water Wetter (available at most major auto parts stores) that will further enhancing the cooling of your engine.  With that higher water ratio and the Water Wetter, that should be ok in your engine even if the temperature in your area drops below freezing in the winter.  But you could always drain a few quarts on that mixture in the winter and replace those quarts with straight anti-freeze with ensure your engine will not freezing up.
Good luck!