Mitsubishi Repair: Overheating problem, mitsubishi eclipse gs, radiator hoses

Question
Hi, i have a 1995 mitsubishi eclipse GS, 2.0, non turbo, 5 speed manual. Since i bought the car, the neddle that shows the car tempeture has always been exactly in the middle and i noticed that all other cars have the  neddle a little bit below the middle. I never did anything about it and since last week,my car has that neddle a litlle bit above the middle and if i turn on my air conditioning, after a while, that neddle will go even higher, almost overheating the car completly. I thought it could be the thermostat, but i had it replaced 6 months ago. So, i don't know why the car temperature is suddenly higher, i don't know why it overheats when i have the air on and i don't know if its normal for the temperature to be ecxactly in the middle. So, any help would be appreciated, thank you very much.
Marcos

Answer
Marcos,
One of the most common causes for overheating is dirty and inadequate coolant levels.  If you let your engine cool down, twist off the radiator cap.  If you squeeze the upper radiator hose and it feels empty and you do not see any coolant by the mouth of the radiator cap housing, you're low on coolant.  But if you do see coolant, but it looks rusty brown or orange in color, you have dirty coolant.  Every two years you should be flushing your coolant system.  This is especially important the older your car gets to prevent coolant system failures.  As rusty coolant circulates thoughout your engine, it deteriorates internal engine components, rots hoses from the inside out, and overall decreases the life of your engine.  So a coolant flush would be beneficial.  You should also consider replacing the radiator cap and upper and lower radiator hoses.  

Inspect your radiator for broken fins and excessive debris that could be clogging airflow.  The less air that is allowed to pass over the radiator, the less efficient it will be at cooling the engine. If the radiator has excessive damage, it should be replaced.

Running the A/C can cause your engine to run hotter only if the above items I've mentioned are not functioning properly. There are a couple main causes.  First, when you turn on the A/C, the A/C compressor is activated, and this puts an extra strain on the engine.  The engine has to do more work to allow the car to run properly under normal conditions.  Second, the AC system contains a condensor unit (looks just like a radiator), which helps cool the refrigerant as it circulates through the AC lines.  The condensor is actually placed right in front of the radiator.  So when the AC is on, warm refrigerant is passing through the condensor to help cool it down.  That warm air also passes over the coolant radiator as well, which can hinder its cooling effect.

If getting the items I've mentioned serviced still does not fix your problem, you should consider having your water pump replaced.  Though the replacement of the water pump requires the removal of the timing belt (which should be changed every 60,000 miles) and that can be labor intensive.  If you're nearing or have gone over the 60,000 mile mark since your last T-belt replacement, I'd recommend having that done and the water pump replaced as well.
Good luck!