fan squealing

[clintondkid]

My 1997 BMW Z3 has a loud squeal near or above
the glove box. Does anyone know what this fan is for and is there a diagram or part number so I can replace it.

[Tigershark48]

Sounds like your heater fan. Does the squeal go away with the fan off? If so, search this forum for heater fan.

[daven]

There's a little computer cooling fan for the ECU behind the glove box. Might be that if the noise doesn't change with the heater fan control.

[saneesh8]

That ECU fan was dead on my car. Don't know that's why it killed the ECU slowly and finally i had to replace the ECU (DME). It pulls air from the passenger compartment (passenger foot area). It is kind of like CPU cooling fan in desktop PC.

[rasmuw]

It could be the emission control (also called secondary) air pump in the engine bay, although that should only be on for few minutes when the car is started and the engine is cold.

[Adker]

The secondary air pump come on during a cold start and one runs a couple of minutes. The E-fan runs to cool the ECU and runs all the time when the car is warm. Here is what I have found, the stock fan new price is way too high. I found a post where a ball bearing (longer life, quite) sub was found for a fraction of the OEM price. This is interesting to me as I know fan failures are very common with age and I don't want to cook my ECU, so I am replacing mine. Links follow, good luck!!

Diagram: http://www.realoem.com/bmw/enUS/show...diagId=12_1009

OEM Part...high $$$: https://www.turnermotorsport.com/p-1...uine-bmw-part/

Substitute fan: https://www.newark.com/ebm-papst/622...vdc/dp/86K9902
https://www.digikey.com/product-deta...SABEgL6nPD_BwE
https://www.alliedelec.com/ebm-papst...SABEgLUIPD_BwE
https://www.mouser.com/ProductDetail...Qk7mzqQA%3D%3D
https://www.arrow.com/en/products/622h/ebm-papst

Link to sub fan source: https://www.bimmerforums.com/forum/s...3#post23888903

[rasmuw]

The secondary air pump come on during a cold start and one runs a couple of minutes. The E-fan runs to cool the ECU and runs all the time when the car is warm.

True. While I think it's not likely to be the secondary air pump, the OP didn't reveal the duration of the squeal.

[Tigershark48]

Great information on the more robust, low cost ECU fan. I’ll be swapping mine for future insurance against ECU failure. Sounds like an easy replacement. Already removed the viscous clutch fan to avoid potential damage. Why wait for something to fail when there’s documented history?

Thanks.

[clintondkid]

Do you know any links that show how to remove and replace the ecu fan. I ordered one today from your links.

- - - Updated - - -

My email is clintondkid@aol.com

[Adker]

To the original post, the secondary air pump and the ECU fan are side by side, should be easy to hear which one is making the noise just by popping the hood. As suggested, changing the speed on the Heater/AC fan will also help narrow down the source.

I went out to the garage and looked at what it would take to replace the fan. Good news, bad news. Note my car is a 1998 Z3M, appears all Z3 use a similar setup. Please post your cars setup so we can be sure.

The Good.
After loosing the screws (they stay secured to the lid) that secure the lid to the ECU box, you can look down at the bottom of the box and clearly see the fan. The temp was 40F and it ran as soon as I turned on the ignition. When removing the lid, be aware there are two round rubber seals between the box and the lid that have to go back on. I posted several sources for the fan since vendors stock will change, check that they are not back ordered or you may wait for awhile.

The Bad:
The ECU will have to be pulled (remove leads to battery first) and the box pulled out of the car to get to the fan mounts on the bottom of the box. Looks like the box slide into slots on the cars metal frame. As soon as I get the replacement fan in, I will post on the R&R procedures in a new post.

Links that supply info on fan:
http://forums.pelicanparts.com/7288915-post2.html
https://www.bavauto.com/media/import...ges/ins227.pdf
https://www.pelicanparts.com/BMW/tec...nt_Systems.htm

[rasmuw]

Great writeup, Adker. Thanks for the links to cheaper fans.

[Adker]

I am glad it helped.

One thing that I still have to understand is the airflow in the ECU box. There is a rubber plenum attached to the fan, feels rectangular and flat, that goes towards the firewall. If the fan is pulling air from the inside of the car, how does it get out of the box? I noticed a little dust on the fan blades so there appears to be no filter on the air intake. Something to look at when I pull it apart.

[Tigershark48]

Can you just feel for air blowing out anywhere around the box? I would, but mine’s in storage.

[Adker]

Good suggestion, I went around the box with the fan running and didn't feel any air. Pinched off the rubber air input to the fan and you could hear the fan slow down.

Found a picture, looks like there is an exit port on the bottom of the box. Picture show the box with the bottom facing up. Red circle is were the fan screws are located and you can see the air intake plenum behind them.

[Tigershark48]

Any idea what this ventilation hose does? If incoming air is from the passenger compartment, maybe this is output air.

http://www.realoem.com/bmw/enUS/show...diagId=12_1009

[Adker]

Just posted a picture of what my box looks like, Slight different box in the Z3.

https://www.allmagautoparts.com/prod...01433118-e36-7

[Tigershark48]

Not seeing a picture in your post.