fan clutch question

[michael89156]

Should fan be running when first starting up the car, [97 318ti] ?? Or should it start up when engine heats up or we turn on air conditioning?? We suspect a bad fan clutch, fan runs non stop from the moment car starts, until we shut off ignition.

[Jeron]

A mechanical fan runs continuously. The clutch helps protect it from engine vibration, high RPM and sudden changes in RPM.

Use a piece of rolled up news paper to try and stop the fan. If the clutch is good the fan should bat the newspaper away easily without slowing.

[michael89156]

I should have mentioned it is an electric fan. It comes on when turning key without even starting engine. And stays running the whole time car is running. I was wondering if this in normal? Or should it just kick in when engine gets warm? Perhaps a bad sensor causing it to run all the time? Is that temp sensor located on side of radiator the one that controls the electric fan?

[michael42775]

I'm not sure what sensor controls the auxillary fan but it should not be running all the time. The electric fan in front of the radiator only should come on when the car is warm or the ac is on. I'd check the sensor's. also trace the wire's. it almost sounds like someone might have bypassed a bad sensor and wired it direct to the fusebox so it comes on with the ignition. Jeron or Wayne can probably tell you what sensor it is. you can also try realoem.com for a diagram. Good Luck!

[Jeron]

You said bad fan clutch, which is why I thought it was a mechanical fan. There is no fan clutch on an electric.

IIRC, the sensor on the side of the radiator controls both the primary electric fans and aux fans.

My first guess would be a relay stuck open. I would think a bad fan temperature sensor would turn on the aux fan as well.

[ellisjay2]

My fan from, what I've been told on my 18is, (95) is supposed to run continuously or is it, (mechanical) I can reach in and stop the fan while engine is running, but the cooling system operates fine, engiine does not over heat, its been this way for bout a year, I wander does my fan operate at driving speed, but im not sure, if I need to I want to go ahead and change my clutch for proper operation.

[coolbear1]

Your electric fan (aux fan) Will run continuusly if the a/c is on. Otherwise it is controlled from temperature sensors feeding information to the engine control module. The ECM sends a signal to the fan relay.

[Jeron]

Originally Posted by ellisjay2

My fan from, what I've been told on my 18is, (95) is supposed to run continuously or is it, (mechanical) I can reach in and stop the fan while engine is running, but the cooling system operates fine, engiine does not over heat, its been this way for bout a year, I wander does my fan operate at driving speed, but im not sure, if I need to I want to go ahead and change my clutch for proper operation.

If you can stop the mechanical fan then the fan clutch is bad. A bad fan clutch will make you overheat in some situations. Fix it. It isn't worth the risk.