FYI: Mechanical Fan to Electric Fan Swap

Originally Posted by delmarco

The only big black question mark that was never understood was:

Why did the BMW Steptronic Automatic cars all come with two fans up until around 2006?

The possible answer or best anyone could come up with was the Steptronic Automatic transmission required some extra cooling hence the extra fan.
But the question still begs is why did BMW abandon the fan in 2006 with the advent of the E90 and the E60 M54 engine facelift? Did they realize the extra fan was not required?

Terraphantm a while back found some pertinent information relating the relevance of having a second fan to regulate transmission temperature since M3 cars all have the two fans.

But that discussion was not followed up because candidates doing the swap are not doing it on an M3.

As for M54 engine transmission cooling and long term effects I can't say.

Kpeng is the only member I know whom has driven with this mod in his car the longest and he has driven his car daily for a number of years in the hottest/most humid place in the USA (Florida). Another member has driven for over a year in Phoenix Arizona, the hottest/driest place in the USA, with this mod and had no issues.

Both claim that they had no issue with engine temp or tranny temp in all that time so based on their experiences I don't think it will be an issue for anyone living and driving in cooler regions.


The AC compressor is not driven by the fan but it is driven by the fan belts. In theory the AC compressor should perform slightly better because we are removing about 5+ lbs out of the belt drive system when we remove the mechanical fan.


Said and done the entire DIY is 1000000% reversible if after a couple of days you find your car is going bananas. Even if you can't return/refund your electric fan after changing your mind you can sure sell it on eBay for easily what you paid for it.

Also the DIY pays for itself when you sell your old mechanical fan and aux fan assembly. Both on their own each are easily worth $75 to $100 and carry a high demand.

Olaf - although newer automatic cars use an electric fan, they use a more powerful one than found in the manual cars. 600W vs 400W.

Does it make a difference? Based on the experiences posted here, maybe not. However, those who live in extreme climates (Saudi for example) should monitor their trans temps

Ok sorry but I am a bit confused. Removal of the auxiliary fan is required to make room for the replacing of the mechanical fan to new electric fan. Would it be possible to run the aux fan with the electric fan? My car makes a horrible bus noise in heat/stop and go traffic and I've already had the fan clutch replaced recently.

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The bus sound comes from the aux fan. You have to remove it anyways so it won't block airflow to the radiator. It is impossible to run both at the same time because there is only one connector that can be used.

Originally Posted by Solidjake

The bus sound comes from the aux fan. You have to remove it anyways so it won't block airflow to the radiator. It is impossible to run both at the same time because there is only one connector that can be used.

So will running one electric fan get rid of the bus sound, and also provide effecient cooling to my auto trans?

Yes. Look at my thread for the DIY

http://e46fanatics.com/forum/showthr...735&highlight=

I did this swap a few weeks ago. Engine temps and everything are fine. But, in the last couple of days, I started to notice a wobbling and vibration coming from the newly installed electric fan. I opened it up, removed the fan and found that one of the little torx head bolts that hold the fan itself on to the fan assembly was missing and the other two bolts were loose. Yikes! That was a disaster waiting to happen. Probably woulnd't have been nearly as catastrophic as losing a mechanical fan but bad nonetheless.

Luckily, I found the missing bolt just laying on my garage floor so, I tightened them all up and it's now fine.

Moral of the story: before installing your new electric, be sure to firmly snug down the bolts.

Originally Posted by eweis

I did this swap a few weeks ago. Engine temps and everything are fine. But, in the last couple of days, I started to notice a wobbling and vibration coming from the newly installed electric fan. I opened it up, removed the fan and found that one of the little torx head bolts that hold the fan itself on to the fan assembly was missing and the other two bolts were loose. Yikes! That was a disaster waiting to happen. Probably woulnd't have been nearly as catastrophic as losing a mechanical fan but bad nonetheless.

Luckily, I found the missing bolt just laying on my garage floor so, I tightened them all up and it's now fine.

Moral of the story: before installing your new electric, be sure to firmly snug down the bolts.

Oh, it would have been nearly as catastrophic as losing a mechanical fan because it would have kept running until it ruined the blades, and possibly burnt out the motor as well.
Then, of course, you would have had a hard time convincing anyone that it was a manufacturing error, since they would have had that old reliable position that you installed it yourself, rather than having it done by a trained BMW Technician (who probably would not have done it, since it was not the intended use for that fan).
So, you would have been out $500+ once you replaced the fan, plus whatever damage it managed to do on its way out.
You got lucky by finding that as soon as you did.

Eweis, it might be a good idea to take it out again and put some thread loctite on the torx bolts, just in case. While unusual, if they backed out once, they might back out again.

Alright I installed the electric fan, runs great engine has less lag and runs slot smoother. But it Just so happened that right after finishing the swap, I get a gearbox error code and am now having hard down shifts and overall rougher shifts in lower gears. Coincidence?

I highly doubt that it overheated if that's what youre thinking, check your mass airflow (pretty sure thats what it's called) the mesh sensor immediately after the airbox

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Originally Posted by nbesheer

I highly doubt that it overheated if that's what youre thinking, check your mass airflow (pretty sure thats what it's called) the mesh sensor immediately after the airbox

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I checked the maf already thinking that could be the problem because I ran the car after swapping the fan in without the maf to test out the fan.

Originally Posted by J1Productions

I checked the maf already thinking that could be the problem because I ran the car after swapping the fan in without the maf to test out the fan.

What does the MAF have to do with the Fan Swap and the Tranny?

J1 did you may be try to put back in the mechanical/aux fan combo and drive around to see if the gear symbol goes away?

That would be your best bet at troubleshooting.

Originally Posted by delmarco

What does the MAF have to do with the Fan Swap and the Tranny?

J1 did you may be try to put back in the mechanical/aux fan combo and drive around to see if the gear symbol goes away?

That would be your best bet at troubleshooting.

Haven't tried that. I could, I actually only took the mech fan out and dropped the electric in. Haven't gotten the auxiliary fan out yet cause I don't have a torx 50.

Originally Posted by delmarco

What does the MAF have to do with the Fan Swap and the Tranny?

Well some people remove the airbox/maf combo for more room or w/e. Not sure why but removing the maf some how throws the transmission gear symbol thing.

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Originally Posted by J1Productions

Haven't tried that. I could, I actually only took the mech fan out and dropped the electric in. Haven't gotten the auxiliary fan out yet cause I don't have a torx 50.

I would think that your not getting sufficient airflow because the Aux fan is in the way. I would say get that off asap and see if that helps.

I'm very close to pulling the trigger on this DIY, just have some maintainance to take care of first.

Originally Posted by J1Productions

Haven't tried that. I could, I actually only took the mech fan out and dropped the electric in. Haven't gotten the auxiliary fan out yet cause I don't have a torx 50.

ooooooooooooooooooooooooooooo....

You can't really do that.

Dude you MUST take the little Aux Fan out or you will mess up your engine if you run both those fans at the same time!

Originally Posted by nbesheer

Well some people remove the airbox/maf combo for more room or w/e. Not sure why but removing the maf some how throws the transmission gear symbol thing.

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oh okay. I didn't know that.

I thought the Large electrical fan that replaces the mechanical fan plugs into the Aux fan plug. How could you run both fans together?

I could see the Aux fan impeeding the flow being a issue thou.

+1 you can't run both at once, only what the connector is plugged into.

Originally Posted by Solidjake

+1 you can't run both at once, only what the connector is plugged into.

+2
This is why some people shouldn't DIY. They mess up their cars and blame us for them not being able to read our DIYs.



It is written clear as day several times in Kpengs, SolidJakes and Nervous threads that you CANNOT have the aux fan in the car at the same time as the electrical fan! Even if the Aux Fan is plugged out it will block air flow, ruin your engine cooling and mess up your car eventually.



Electric Fan replaces BOTH Mechanical Fan and Aux Fan.Meaning BOTH Mechanical Fan and Aux Fan MUST BE REMOVED FROM THE VEHICLE before the Electrical Fan is installed and turned on!

The tribe has spoken.

[QUOTE=delmarco;14619770]+2
This is why some people shouldn't DIY. They mess up their cars and blame us for them not being able to read our DIYs.



It is written clear as day several times in Kpengs, SolidJakes and Nervous threads that you CANNOT have the aux fan in the car at the same time as the electrical fan! Even if the Aux Fan is plugged out it will block air flow, ruin your engine cooling and mess up your car eventually.



Electric Fan replaces BOTH Mechanical Fan and Aux Fan.Meaning BOTH Mechanical Fan and Aux Fan MUST BE REMOVED FROM THE VEHICLE before the Electrical Fan is installed and turned on!

Your cool.