I am trying to hunt down the reasons for my 1992 740 wagon running hot. I have found the electric radiator fan does not roar up or turn on when I start the motor. In fact I can only recall hearing it come on as the motor seems close to boiling over. Indeed the roar of the fan seems to be associated with the sickly sweet smell of coolant. Is this fan supposed to roar or start as the motor is turned on? I read the FAQ and was not sure about that. I went outside and watched the motor idle for a good 15 minutes and it never turned on. A few hours later I went out and started the motor, turned on the AC and the fan started right up. As soon as the AC was turned off the fan went off. Where do I start with this fan to see what is wrong with it. I think it is a recent (last 5 years or less) replacement by the original owner. I am fairly ignorant of cars so please feed it to me straight and easy. Thanks in advance.