[Bali]

Electric fan is not working.

 

[Bali]

On the E46, the electric fan is the primary cooling fan and absolutely must be working properly. Overheating at idle is typically because the electric fan has failed.

Your automatic transmission E46 has a "pusher" electric fan in front of the radiator. All but the earliest manual transmission E46s have a "puller" electric fan behind the radiator and no mechanical fan.

Check that your electric fan is running when the engine temperature rises above normal.

Read BMW-North's Electric Fan Guide for all the details.
https://drive.google.com/file/d/1BMHsmEwoEuSPkOuTpuLRnETy1XTielvZ/view?usp=drivesdk

 

[Bali]

There's your answer, whether you have a functioning fan clutch or not.

Agreed. The electric fan is critical on the E46. You WILL overheat if it’s not working.

The mechanical fan and clutch is not really needed actually, but that’s a different debate.

 

[Bali]

your pusher fan should be acting as a backup to the mechanical one.

Sorry Don, but this is incorrect. The electric fan is the primary cooling fan for the M54, not a backup. If the electric fan is not running at idle, as in OP’s case here, the coolant WILL overheat. I can guarantee OP’s mechanical fan and clutch are NOT the problem here. You can remove the mechanicl fan and clutch and the engine will stay cool at all speeds if the electric fan is working properly.

 

[Bali]

Somebody recently posted a link to an article on these fans,

I posted a link to BMW-North’s Electric Fan Guide back in post #9 above.

Overheating While Idling

I have an Automatic 2000 323i, it overheat while idling. The temp. gauges slowly start to creep up but goes down to when I turn on the heat at full blast. I recently (last three weeks) changed the following: 1) Radiator 2) Expansion tank kit 3) All hoses 4) Heater pipe 5) CCV kit 6)...

www.e46fanatics.com

It explains how to test the electric fan, common failures, etc.
The fan motors seem to be pretty robust. The control unit is what usually goes bad.

In OP’s case here, the electric fan only runs when the AC is switched on, but doesn’t run when the AC is off even though the coolant is overheating.

 

[Bali]

Discourse is good, disagreement is fine, and I’m always open to new info. I still stand by my comment that the E46 electric fan is the primary fan and must be working properly to prevent overheating. Unplug it and drive around for a bit to see what happens. Earlier BMW models may be different. Regarding the pusher vs puller electric fans, they are the same, except the blades are slightly different.

Regarding OP’s problem, I think he should first read the electric fan guide I linked, then focus on why the electric fan does not run with AC off when coolant starts to overheat.

 

[Bali]

That would make sense if there’s reduced coolant flow, an inaccurate sensor, the fan isn’t running, or something else...

I’m still stuck on the fact that the electric fan only runs (and the engine does not overheat) when the AC is switched on. If OP leaves the AC on so the electric fan runs, it doesn’t overheat (from what I’ve interpretted so far). I think OP needs to figure out why the electric fan isn’t running with AC off. OP just needs to read through the electric fan guide and check all the signals that turn on the fan, the fan speed, etc. INPA would make this quite easy.

 

[Bali]

The heater pipe busted, and it overheated the car. Then the radiator cracked by the drain screw. The rest of the items were replaced as preventative since I have everything open.

I missed this post earlier. OP may have a blown head gasket. Let’s see what his shop says.

 

[Bali]

~ 90° Celsius, not F

I’m just impressed you got the little degrees symbol in there!

 

[Bali]

Throwing this in here for funsies...

 

[Bali]

so what did this shop find out?

Prediction: their estimate will be at least $1,500.

 

[Bali]

Glad you got it fixed, thanks for posting the solution. That was a tricky one!
Did the shop fully clean out all the stopleak? I’d worry about other issues like the heater core having blockage.

 

[Bali]

One way to see is it to log coolant, oil, and ATF temperatures with and without the electric fan plugged in. That clearly shows how critical it is. When the engine is at operating temperature and the car is still, the coolant temps will start rising with the electric fan unplugged.

 

[Bali]

that sounds like it would be a good indicator.
I would think BMW_North or Terra have this info already?
wish they would chime in with what they know.

so Bali you on vacation..noticed your “location” flag has changed.

I did those logs years back using the Testo program, but I cannot find the log files. I think they were on a backup NAS that died.

I’m still in SoCal, was just testing out the Location info. I’ll fix it.

I reached out to BMW-North but got no response. I need the full version of his Electric Fan Guide so I can share it.
I think TerraPhantm confirmed the electric fan control maps are the same between MT and AT cars, which would be enough for me. He may be busy right now, but he’ll be back at some point (I hope).

 

[Bali]

BD - Full version of Electric Fan Guide here:
BMW-North Electric Fan Guide

Thanks! I updated the link under IMPORTANT THREADS & LINKS.