My car is a 1990 Volvo 740GL. It's recently started to overheat. I noticed the problem was only when the car isn't in motion, and tonight have narrowed the problem down so that I know it will only start to overheat when the engine is idling. When I maintain 2000 (or so) rpms (moving or sitting still), the temperature of the engine will be steady and normal. If the rpms drop, the temperature will start to creep up. Other sources of information indicate that this could be because of a broken or failing water pump, broken or failing thermostat, or the car is simply low on water. The water pump has been replaced in the last five years, and the thermostat has been replaced within the last year. I'm hoping it's just low on water, and so I come to my first question. Q1: When I check the water level in the car, should the engine be cold? Q2: A manual indicates that when flushing the radiator, the air conditioner temp. switch should be set to Hot, do I also need to switch it over to Hot when checking the water level? Q3: What else could be causing the overheating problem? Where I am it's been hot this summer, and the mornings are just starting to get cool, if that could affect it. Thanks for any information.