Volvo: overheating volvo, but enough coolant, volvo 240, transmission levels

Question
My volvo 240 stationwagon has never liked sitting in traffic etc, but it just got a lot worse today. We were on a roadtrip with quite a bit of stop and go traffic and you can hear the car making this humming sound, then it just doesnt want to go or dies if sitting at a stop light and it seems incredibly hot. We turned on the heater to try and help the problem. I checked the coolant, oil, transmission levels and all are fine, and the gauge isnt going up either so it's like nothing is apparently wrong with it, but there is.

Answer
Claudia,
First you need to be sure that the engine is overheating. Test it with a temp gun at the t/stat when the problem occures. If it is not, then trace the humming noise. After finding that humming, repair that and see if the car still has a loss of power. Problem might be the main fuel pump is working harder then needed because the in tank pump is not working or fuel filter is blocked.