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Old 11-05-2011, 04:22 PM   #1
delmarco
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Cool Everything YOU need to know that I know about the E46 Engine Fans! PICTURES



A. The MECHANICAL FAN sits naked inside the engine bay and hangs off the engine block. It is always on from the minute you turn the key to start the engine. It stays on all the time until the engine is turned off. It always spin at the same speed coinciding with the belt drive system. It is attached to engine via the water pump and is also connected with the belt drive system. This fan directly cools the engine and is usually quiet. This is the fan that tends to explode from a bad water pump bearing (i.e infamous water pump wobble) or cracked blades. This fan is driven by the belts in the belt drive system which means that this fan will NOT work if the belt drive system pulley components seize up, engine belts break or alternator seizes.



The belt drive system also includes as shown in the picture above the power steering pump (D), idler and tension pulleys (respectively C and B), alternator (I) water pump pulley (A) and AC compressor (F).



Although the mechanical fan is connected to the same belt drive system that the AC Compressor is connected to the mechanical fan has nothing to do with AC coldness or strength. However the reverse is sort of true. When the AC is turned on in the cabin the effect of the AC compressor turning on is rippled thru the belt drive system and will be demonstrated as a momentary roughness in the engine rpm (i.e the rpm needle on the odometer jumps).

B. The AUXILIARY FAN sits in a plastic enclosure outside the engine bay. It is located in front of the radiator right behind the nose panel's kidney grills where it can be seen thru from the outside whiles looking thru the grills at the front of the car.

This fan is usually off for the most part and only turns on for brief intervals at a time to assist in extra cooling during times of high engine load and hot weather engine idle especially during congested summer traffic.

This fan primarily enhances cooling to the radiator zone by pushing cool air into the engine from outside the kidney grills.



Because of its location the Auxiliary Fan does not directly cool the engine block the way the mechanical fan does.

The Auxiliary fan when it comes on can be super loud (ie. the infamous UPS/FedEx Truck sound) and annoying.

This fan is not attached to belt drive system and can still work if the belt drive system fails. However, it is an electrical powered fan and depends on the alternator and battery for power.

The Auxiliary fan has absolutely nothing to do with enhancing the AC Compressor or AC coldness/strength as felt inside the cabin. However the reverse is true as when the AC Compressor/AC is on during engine idling this fan will come on only to assist in extra cooling to the radiator and engine bay.

Because the steptronic transmission's cooling lines run to the radiator this fan is thought of to also enhance transmission cooling on steptronic/automatic cars.



C. The ELECTRIC FAN as it relates to the E46 originates ONLY in manual transmission cars (except M3) from 1998 to 2006. The electric fan has now also permanently replaced the mechanical fan as the sole main engine cooling fan on all modern era BMW cars from 2005/2006 to present.



On the E46 this fan sits in a plastic enclosure inside the engine bay between the back of the radiator and empty space in front of the engine. It cannot be seen from outside the car thru the kidney grills and it works to "pull in" cool air from the front of the car into the engine bay. This fan is usually always quiet and on.

The ELECTRICAL FAN, on the manual cars, can be said to replace both the MECHANICAL FAN and AUXILIARY FAN by directly cooling both the radiator and engine bay zones. So one electrical fan in theory will provide the same cooling performance as the mechanical fan and auxiliary fan.This fan is not attached to belt drive system and can still work if the belt drive system fails. However, it is an electrical powered fan and depends on the alternator and battery for power.



NOTE ABOUT THE FAN DELETE MOD: This should really be called the one for two fan replacement mod because at the end of the mod your steptronic/automatic E46 car will have the exact one electric fan set up that the manual cars all have.


When done correctly the electric fan has been successfully transplanted to replace both the original mechanical and auxiliary fans on steptronic/automatic E46 vehicles.

It is important to understand that for the electrical fan to work properly both the original mechanical and auxiliary fans MUST first be removed, or deleted, from the car.

When said and done the newly installed electrical fan will use the same connector that the auxiliary fan uses and, because it is mounted on the inside of radiator support frame, the electrical fan will sit in the same engine bay space that the mechanical fan occupied before the modification.

Although disputable, the swap is said to alleviate the weight burden and parasitic drag* that the mechanical fan puts on the the belt drive system and water pump. This lack of weight is said to improve MPGs and add performance in HP. Removal of the auxiliary fan is said to make the car run quieter and smoother.

Engine cooling/performance, transmission cooling/performance as well as in cabin AC cooling is not affected in anyway by the removal of the two fans and the swapping in of the one electrical fan. *

Said and done, the hard fact remains that the one electrical fan actually can replace both the mechanical fan and auxiliary fan on the steptronic automatic e46 cars.

The Fan Delete Mod is NOT recommended for the M3 cars!





____________________________________________________________ ______________________________________________
FOOTNOTES:


Much Thanks and Deep Respect to Nervous and SolidJake for the pictures and Kpeng for the original Fan Swap inspiration.

* This opinion of parasitic drag of the fan on the rest of the belt system is debatable because the fan doesn't power the system but the system powers the fan. Also it has been argued that the system is already designed to be balanced with the fan mounted off the water pump so removing a component from the system shouldn't improve much if anything.

However, it can be counter argued with an astronomy example of what would happen to the sun's rotational speed if one or all of the planets were to instantly vanish.

Although the mass of the planets combined is insignificant to the mass of the sun there is still some rotational drag that the planets have on the rotational speed of the sun even though the sun's mass is what powers the solar system rotational speed.

So removing about 5lbs from the belt drive system should have some considerable affect on the system's performance even if it is tiny.


* Kpeng (Florida), Solidjake (NY) and a few other members who drive daily in Arizona have claimed that the engine cooling, transmission cooling/performance and in-cabin AC cooling in their cars has not been hindered in anyway by the electrical fan swap whiles driving in extreme heat conditions.

Last edited by delmarco; 11-06-2011 at 01:39 AM.
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Old 11-05-2011, 05:36 PM   #2
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Old 11-05-2011, 06:35 PM   #3
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As always.. A very nice and thorough post. Much appreciated.

And, a Big thanks to all the previous members who started and contributed to the information!
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Old 11-05-2011, 06:45 PM   #4
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Very informative. Sad that it's not recommended for M3s.
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Old 11-05-2011, 06:50 PM   #5
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Awesome post... Now about that electric fan, wheres the best place to buy? My car's fans definitely need to be replaced.
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Old 11-05-2011, 07:01 PM   #6
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Quote:
Originally Posted by HyeWarrior View Post
Awesome post... Now about that electric fan, wheres the best place to buy? My car's fans definitely need to be replaced.
Thank.

Most members have purchased the BEHR fan off eBay which costs around $185. I'm sure other sites may sell the BEHR fan but where ever you go BEHR is the brand you want to get and its OE.

Also the beauty of it is that you can sell your old fans, providing they are in good working condition, for a sizeable fraction ($100 and up) of what the one new electric fan costs.

If you are lucky with the resale of your current fans then the DIY could cost you zilch.

That said, the fan delete mod is 100% reversable if you decide to change your mind and you can sell back the BEHR fan you just bought easily and quickly for what you paid for it.

all and all when I do this on my car this season it has potential for being a good DIY.
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Old 11-05-2011, 07:09 PM   #7
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Do you have to remove front bumper to remove aux fan? What kind of pain in the ass is that to do?
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Old 11-05-2011, 07:10 PM   #8
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[QUOTE=delmarco;13769827
Although the mechanical fan is connected to the same belt drive system that the AC Compressor is connected to the mechanical fan has nothing to do with AC coldness or strength. [/QUOTE]

Nice writeup.

Might want to be alittle clearer here. You make it sound like the fan is connected at the crank that drives the belt for the A/C. The mechanical fan is attached at the water pump pulley, not the crank.

Same belt System -- Technically yes
Same belt "loop"-- No

I could see where some people might be confised by this.
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Last edited by GCoop; 11-05-2011 at 07:12 PM.
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Old 11-05-2011, 07:19 PM   #9
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You know your going to get asked for the part number.
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Old 11-05-2011, 07:39 PM   #10
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Quote:
Originally Posted by GCoop View Post
Nice writeup.

Might want to be alittle clearer here. You make it sound like the fan is connected at the crank that drives the belt for the A/C. The mechanical fan is attached at the water pump pulley, not the crank.

Same belt System -- Technically yes
Same belt "loop"-- No

I could see where some people might be confised by this.
I actually was looking at that sentence after I wrote it and edited that sentence a few times. I had originally re-edited it to say:

"...connected to the belt system and to some extent the AC Compressor..." but then I changed it back.


Indeed it is not directly connected to AC Compressor's mini belt loop but when you study the belt drive system you will see the same drive pulley drives both belt loops. So it is all connected and I left the sentence like that.

lol. I knew someone would catch that.
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Last edited by delmarco; 11-05-2011 at 07:58 PM.
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Old 11-05-2011, 09:30 PM   #11
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Thanks for this. For those with automatics that have done the swap, do you notice if the electrical fan stays on all the time or does the fan behave in the same manner as it did with the original mechanical/pusher fan setup, coming on when engine is under extra load, with A/C on, etc.

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You know your going to get asked for the part number.
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Old 11-06-2011, 12:49 AM   #12
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Old 11-06-2011, 01:27 AM   #13
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Nice writeup, just a few pointers :

It is always on from the minute you turn the key to start the engine. It stays on all the time until the engine is turned off. It always spin at the same speed coinciding with the belt drive system.
* It's run of a visco clutch that varies the power transferred with the heat going through it (that is it wont spin as fast on a cold engine as a hot one)
The belt drive system also includes as shown in the picture above the power steering pump (D), idler and tension pulleys (respectively C and B), alternator (I) water pump pulley (A) and AC compressor (F).
* Dont forget the crank pulley

The ELECTRIC FAN as it relates to the E46 originates ONLY in manual transmission cars (except M3) from 1998 to 2006.
* In the us that might be true , not in europe though(my car came with AUX/Mechanical stock for example)


Also not that the fan output from the DME will activate when the lower rad hose sees temps above 90'C(194F), irregardless if you have a AUX or Radiator fan connected to the output.
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Old 11-06-2011, 01:41 AM   #14
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Quote:
Originally Posted by Pir4t View Post
Nice writeup, just a few pointers :


Also not that the fan output from the DME will activate when the lower rad hose sees temps above 90'C(194F), irregardless if you have a AUX or Radiator fan connected to the output.
hey what is the "radiator fan"?
is that another term for the aux fan?

asking because i keep seeing that term "radiator fan" used on a couple of threads.
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Old 11-06-2011, 01:59 AM   #15
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Originally Posted by delmarco View Post
hey what is the "radiator fan"?
is that another term for the aux fan?

asking because i keep seeing that term "radiator fan" used on a couple of threads.
The term radiator fan is used when talking about a fan attached to the radiator(i.e. SPAL Fans, Elextric fan as you called it)
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Old 11-06-2011, 02:01 AM   #16
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So, is this fan more powerful than the one that comes in the M/T cars? If not, then I wonder why BMW went to the trouble of having two different configurations for the e46. Why not simplify things with one design? And if it is more powerful than the M/T fan, I wonder why they did not just use one stronger fan for both models. It seems odd to have two different configurations, when a simple change could lead to a single design. I suppose some will say it was due to the extra cost, but the complexity of managing two different designs, and the costs of managing the supply chain, logistics, etc would probably outweigh the additional cost per car. I know for a fact that just adding another part number to the bill of materials costs money (more than you would think - anywhere form a few hundred to hundreds of thousands of dollars, depending on the size of the company). I am just curious about BMW's design justification for doing it that way. I doubt I will get an answer here, but I wonder if any BMW techs out there have ever seen anything official from BMW that justifies why they did things this way.*
So, with this modification, do you now rely on the circuitry and logic that kicks on the pusher fan, or is there some modification to that as well? If so,*I would imagine that it is a good idea to replace the sensor that triggers the pusher fan, since a failure of that sensor would knock out your entire fan cooling system - correct?

@Delmarco - thanks for answering the question I posted in kpeng's thread about his mechanical fan delete. I asked if the pusher fan should be removed, but the question was never answered, likely due to my perceived newbie status. But the post was not clear about this, and I thought it was a relevant question.
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Old 11-06-2011, 04:07 AM   #17
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Functional justification... true. But girls dropping their panties counts for something
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Old 11-06-2011, 06:51 AM   #18
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Do you have to remove front bumper to remove aux fan? What kind of pain in the ass is that to do?
Yes, here is my DIY

https://e46fanatics.com/forum/showthr...735&highlight=
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Old 11-06-2011, 07:02 AM   #19
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One of the things to consider on the original mechanical + electrical aux. fan configuration is "backup" in the cooling system, it's not very likely to have both units to fail at the same time.

Even though the mechanical fan can/may fail (in some fashion, either the fan-clutch goes out or a/the fan blades cracking/breaking off) you will still have the auxiliary fan. And, vise-versa...

It's to keep the operation of the cooling system functional more so, than to extract the maximum horsepower out of the motor that is most critical.
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Old 11-06-2011, 07:21 AM   #20
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Do you have to remove front bumper to remove aux fan? What kind of pain in the ass is that to do?
Yes, you do have to remove the front bumper, and while it sounds daunting, it's not hard, and one person can do it. See Bentley or http://tis.spaghetticoder.org/s/view.pl?1/07/20/07 . edit ... or Jakes post above.
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