FYI: Mechanical Fan to Electric Fan Swap

Good information guys.

I'm definitely doing this, not sure when though. Like someone else said, probably won't be until I overhaul the cooling system. Hopefully that will be before it lets go.

Anyways, I'm thinking about leaving the aux pusher in the front, and installing another puller run by a relay on the engine side. I would probably set it to run on high or low anytime the ignition is on. I'm not a big fan of the temp controllers. This won't be the cleanest install, but I'm not sure I trust the single electric fan, like other have pointed out.

I'm sure BMW put both the electric pusher and mechanical puller fans on the automatic equipped cars for good reason (they're not in the business of wasting money). But when we modify our cars, sometimes compromises have to be made. When installing an intercooler into an automatic equipped car, the front electric pusher fan needs to be removed for clearance. This is what we do with the Technique Tuning turbo kits for automatic cars (and replace the mechanical puller fan with a factory electric puller fan).

I have monitored the transmission and radiator temps with both configurations: stock cooling (puller and pusher) and modified cooling (just electric puller). The temperatures have been similar. Likewise, I've monitored the transmission temps with the turbo kit installed, and they were still normal.

In 99% of the cars, this mod will work with no ill effects. Sure, the possibility exists for higher transmission temps, but I haven't encountered them yet.

Originally Posted by ///Flash

Although the OP post is somewhat interesting it is severely flawed and frankly ill advised.

1) Removing the AUX fan just so he can install the intercooler is a mistake at the expense of his tranny. The AUX fan on the automatic transmission is design to kick in when the clutch fan is insufficient at keeping the engine in the normal operating temperature.
When your engine temperature is in the middle it reads between 167°-235.4° F. There is about a 68 degree variation between what is normal. Anyhow, when the OP engine was overheating, he was overstressing both his engine and transmission because it means that the temperature was above 235.4F. Since the automatic transmission used the engine coolant to cool down (via the tranny heat exchanger), this means that the OP's tranny was being over stressed. Any temperature above 200F will decrease the tranny lifespan and I am sure the OP just decreased his tranny life. His tranny is going to die soon.

2) The reason why BMW only install a clutch fan (ie mechanical fan) on its automatic cars is because they want to keep the tranny in its optimum operating temperature. The clutch fan is working to keep the coolant below 200 degrees so that the auto tranny doesn't get overheated. Manual transmission doesn't have a cooler and does not rely on the engine coolant to cool itself so therefore they don't require a clutch fan.

Originally Posted by NickG@TechniqueTuning

I'm sure BMW put both the electric pusher and mechanical puller fans on the automatic equipped cars for good reason (they're not in the business of wasting money). But when we modify our cars, sometimes compromises have to be made. When installing an intercooler into an automatic equipped car, the front electric pusher fan needs to be removed for clearance. This is what we do with the Technique Tuning turbo kits for automatic cars (and replace the mechanical puller fan with a factory electric puller fan).

I have monitored the transmission and radiator temps with both configurations: stock cooling (puller and pusher) and modified cooling (just electric puller). The temperatures have been similar. Likewise, I've monitored the transmission temps with the turbo kit installed, and they were still normal.

In 99% of the cars, this mod will work with no ill effects. Sure, the possibility exists for higher transmission temps, but I haven't encountered them yet.

Nick = The Word.

Also let us not forget that fans are not nessasary when your car is in motion.

sounds like a solid mod but im still inclined to just leave the mechanical fan in mine..the extra amount of cooling in the auto's can only benefit the tranny imo.

I agree with ///Flash, i also notice that the M3s manual and SMG have 2 fans also.
I think the machanical fan because of its placement and design, covers a wider area of the actual radiator, that mean, the bottom end where the tranny cooler is, will be effectively covered by the machanical fans cooling area.
The electrical fan, from what i remember is smaller than the mechanical ones, and does not cover the bottom corners of the radiator (tanny cooler section)

Based on what Nick has said, it seems its a case of overkill on BMWs part, which apprently isnt that much overkill since the fukers still **** themselves.
If anyone is worried about the tranny not being cooled properly with the electrical fan, an auxilary tranny cooler can be added. they can be bought fairly cheap top very expensive. My 6th Gen V6 accord had a similar rep as BMW auto boxes, and i did this to it, and that car is still running with the original transmission.

I think the M3s and autos can safely run electric fans, but as guys have said, its being done by BMW for a reason.
Now the question is, are the E90s and 1 series still using mechanical fans, do they have aux fans? Nick and Ken are both in humid muggy Florida, and running boosted cars, so i think if it works for them, the rest of you will be fine.

It's going to be fine.

Before doing this, I confirmed with several sources. One of which is Nick G, who I'm sure has done his research on it (as he has mentioned). He isn't one of the most respected BMW tuners without merit.

The car has not overheated or had any issues since swapping in the electric fan.

^ theyre not sweating the car engine, theyre sweatin gthe tranny temps. just sayin

Originally Posted by snikwad

^ theyre not sweating the car engine, theyre sweatin gthe tranny temps. just sayin

I understand that. Nick has monitored it and found it to be fine. None of the people "sweatin" it have any proof or first hand experience.

Besides, I'm ok if it blows up anyways. 6 speed swap win.

yep. i read what he wrote, plus they take a crap sooner or later anyway, even on bone stock cars.

Originally Posted by snikwad

yep. i read what he wrote, plus they take a crap sooner or later anyway, even on bone stock cars.

Yes sir. It's at 110,000 miles. Its already exceeded its average life expectancy.

I think I can contribute my 2cents as well.

My aux fan + mech fan were removed for a electric pull fan because of the FMIC.

72 track events, competing in NASA TT for the last 3 years and not a single issue. To top that off, my track ride is a steptronic. Bite me!

Originally Posted by Mr Paddle.Shift

I think I can contribute my 2cents as well.

My aux fan + mech fan were removed for a electric pull fan because of the FMIC.

72 track events, competing in NASA TT for the last 3 years and not a single issue. To top that off, my track ride is a steptronic. Bite me!

you just got lucky!.haha

Originally Posted by Mr Paddle.Shift

I think I can contribute my 2cents as well.

My aux fan + mech fan were removed for a electric pull fan because of the FMIC.

72 track events, competing in NASA TT for the last 3 years and not a single issue. To top that off, my track ride is a steptronic. Bite me!

Even more confirmation.

Do the doubters want to continue?

Originally Posted by Mr Paddle.Shift

I think I can contribute my 2cents as well.

My aux fan + mech fan were removed for a electric pull fan because of the FMIC.

72 track events, competing in NASA TT for the last 3 years and not a single issue. To top that off, my track ride is a steptronic. Bite me!

That auto tranny survived it all? No tranny cooler what so ever? Did you shift or let the car do the shifting?

Originally Posted by EmFiftyFour

That auto tranny survived it all? No tranny cooler what so ever? Did you shift or let the car do the shifting?

I don't believe he runs a tranny cooler.

Why would the shifting matter?

Originally Posted by kpeng

I don't believe he runs a tranny cooler.

Why would the shifting matter?

I've read on many occasions you put the tranny under extra stress when you use the steptronic rather then letting the car do it's own shifting. Think thats bs?

Originally Posted by EmFiftyFour

I've read on many occasions you put the tranny under extra stress when you use the steptronic rather then letting the car do it's own shifting. Think thats bs?

Um...yes.

@EmFiftyFour: yes I have to shift. That's the only way to be competitive. Have a look what NASA TT is about. It's not a drag race.

The short answer is I have a secondary transmission cooler.

The long answer...

From Aug 2003 to April 2006, I tracked my car without a secondary transmission cooler. The only time I saw my transmission temp rise during this period was mainly during summer tracking months. Was the car driveable? Yes. Did it go to limp or un-driveable mode? No. I wrote up a bit on what happens to the transmission control program in my blog. So you can read more there. I have data that dates back to Aug 2003 including track and non-track events.

In April 2006 I installed a secondary transmission cooler. The need for it came because as I started to drive faster around the track, the engine and transmission got a little more beating and of course to deal with summer track events.

Since then and until now, the secondary transmission cooler is used depending on track configuration, ambient temp and number_of_shifts/lap ratio. Why so? Testing months (Dec, Jan, Feb) are usually quite cold here and I'd like to avoid a transmission running with less than desired fluid temperature.

That aside, there are several other reasons why your transmission temp will rise even if you have the aux + mech fans under non-track conditions:

1. Faulty transmission thermostat.
2. Faulty transmission heat exchanger.
3. Filthy/clogged up radiator fins.
4. Coolant leak.
5. Transmission fluid leak.
6. Faulty fans.
7. Faulty water pump.
8. Low coolant level.
9. etc...

So given a healthy cooling system to start, the electric fan mod will be fine for your occasional canyon carvings and highway vrooming.

So this may be a dumb question, but does the removal of the aux fan impact A/C performance (i.e air temp)? I like the concept of the swap, but I like to be comfortable too...

thanks