Radiator fan (electric) help!!

[JES1680]

Hep me please!

2001 330i 5spd. Electric cooling fan, my car doesn't have the shaft driven one.

Overheated:
Replaced expansion tank
Replaced Electric fan as old one did not work when appling 12 volts.

New one does not work either.
I have 12volts at the plug.

I've traced the wiring harness to the firewall and assume it goes to the fuse box. Have 12volts at the plug so I don't believe it's a fuse. There are 3 wires on the fan hot, ground (large wires) and a smaller wire which I'm assuming is the trigger to turn the fan on and off. So I'm guessing there is no relay, just a signal from the computer, so that leads me to a sensor.

There is a sensor in the lower radiator hose, and a sensor in the botom of the expansion tank. One has to be for the guage (which works fine). Not sure which one that is, but I'm guessing one feeds the computer to tell it when to turn the fan on. Any Idea which one and how to test?

I've got a Bently manual on order, but can anyone help me trace this problem?

Thanks for any help.

[JES1680]

Got it figured out.
Needed the correct coolant re-filling procedure. Now fan turns on temp guage stays centered. I was about a gallon low hehehehe..... Oops better get the manual!

[Jeron]

So was it coolant all along and the fan wasn't actually bad?

I finally looked at my 330i auto and confirmed that it does have the mechanical fan. That's an interesting difference between the manual and auto.

[JES1680]

I still belive that the fan is bad otherwise I wouldn't have overheated as I (belive) I had enough coolant in the car. I sure left enough on the ground!

Strange that neither fan would work with 12 volts across the power / ground wires. There is a 3rd wire, but i'm not sure what that would have to do with the fan running if I cross the + and -.
I suppose that I could hook up the old one, but I can't take the new one back and I'm not ambitious right now to try. Maybe over the long cold winter.

I cant' figure out why the auto has the mechanical fan and the 5spd has only electric other than maybe the 5spd is a longer tranny and there isn't enough room.
The new fan is a Bosch and is a different design, wider different blades etc. looks like an upgraded version of what was in there. Hopefully that takes care of my cooling problems until the inevidible water pump failure!

[Jeron]

So the fan went out, it overheated and blew the coolant out; hence the low coolant conditon preventing the sensor from activating the new fan. That sounds resonable.

It could be longery tranny since you said there wasn't enought room for the mechanical fan. I suppose it could be to provide constant cooling to the auto tranny radiator. It it was electric fan the auto tranny fluid would also need a sensor to activate the fan.

[JES1680]

Yep, that's my theory and I'm stiking to it. It's easier to justify the $230.00 fan that way.

All my other BMW's E30 325es, E36 325i, E36M3 (all 5spds) have had mechanically driven fans. Hmm. Got to be a cost or packaging reason for them to change. Of course most (that I've seen lately) new cars have only electric cooling fans. My wifes MB E320 has electric only as well and its the same thing, depending on the year they could have mechanical or electric.

All this water cooled stuff is for the birds anyway, I'm tired of being sticky and smelling sweet. I'm going to drive my 78 911 until the snow files. No coolant issues there!

[Jeron]

You sound like my boss thumbing his nose at the water cooled.

I removed the mechanical fan from my E36M3 yesterday while replacing the oil filter housing. I figure I have a few months before I HAVE to install an aftermarket electric.

I removed it to make the repair go faster and to make my thermostat housing replacement easier, when I get to it. I plan to leave it out for the tiny (6-8) HP gain it is purported give.

[JES1680]

Water cooled isnt so bad. I cut my teeth mechanically with old air cooled motorcycles, so ya go with what ya know. Long before I was a Porsche guy I was a BMW guy, and probably will be long after as well. Although I don't see selling the 911 any time soon. Its been one of the most reliable cars I've had in a long time.