Hi. I have a 97 626. It has overheated yesterday and I was wondering whether this could have been caused by a flat battery, the battery is flat and we had the heating on full at the time. I have since done a mini charge and ran it at 2500 revs for 5 mins and it never went passed the half way temp mark, it sounds fine, the coolant does need a little top up, but the rad is full. Could it be that there wasn't enough juice to cut in the rad fans or something as it does seem to be a bit of a coincidence, or should I be looking for a bigger problem. Thanks.

 

Can't see where a dead battery would cause a car to overheat. But you should figure out why the battery did go flat.

The purpose of the fan is to pull air through the radiator when the car isn't moving fast enough for air to flow through AND the coolant is over a certain temperature. If the car is overheating when driving down the highway the problem isn't with the fan. A common failure with the fan is the water switch. When the car is moving through slow traffic or stopped, the water switch should open causing the fan to run. You can test the fan by disconnecting the wire to the water switch and then starting the car. The fan should turn on immediately. If the fan never turns on when the car is at a stop and the temp gauge is getting warmer and warmer, the water switch is probably bad.

Other causes for overheating are a bad water pump, loose belt, bad thermostat, and low coolant.