Mitsubishi Repair: Mitsubishi overheating, coolant level, radiator core

Question
I have a 1994 Mitsubishi Expo 7 passenger that overheats. The thermostat is ok, and the coolant level is ok. When it sits at idle, it does not overheat. It overheats when driving after about 5-8 miles. Does this sound more like the water pump or a radiator problem?

Answer
Bruce: Are the fan kicking on as they should? I would check the water pump, radiator core to see if it might be blocked or grille restricted, check the electric coolant fan blades to see if they might be broken or cracked, also try replacing the radiator cap as it might not be maintaining the proper pressure and also have the ignition timing checked as it much be off or incorrect. Hope this helps and God bless: Linda