If your tranny is an automatic I recommend you leave the mechanical fan and the aux pusher fan alone. That's how BMW engineers designed it. If the engine get warm is stop and go traffic you need to replace the mechanical fan clutch. Otherwise perform a proven swap to the manual tranny electric puller fan.

 

Thanks. I'm not having any cooling issues, but I do want to get rid of the mechanical if only for piece of mind knowing I wont have to worry about it grenading one day. An electric fan from a manual car is cheap enough, but if the stock auxiliary fan will do the job then that's even easier. I found a Pdf of a BMW shop manual for the fan system that states the fan, motor, and control module are all interchangeable between the pusher/puller fans. The only difference is the shroud for mounting either in front of or behind the radiator. I'm willing to experiment, so for now I'm going to remove the mechanical fan and leave it in my trunk with a couple tools, and do some driving with my scanner hooked up to monitor actual coolant temps. I'll let the coolant temps dictate my decision on switching fans or not.

 

Dude just put in an electrical fan and be done with it. You're not gonna get the correct amount of cooling capacity with a pusher fan. Sure maybe in the winter but as soon as it gets warm you're just gonna have to put the stock one back on or swap it. So why even dick around?


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It literally takes me 5 minutes to take the mechanical fan on/off including reinstalling the shroud and air ducts. With it being so easy, I figure why not test it out. You're right that it's not much of a test this time of year. I pulled the fan and drove around for 30 minutes last night and it never got hot enough for the fan to even kick on. The cars about to be parked for the winter anyway. I'll update in the spring/summer for anyone who cares to know. I just realized how easy it is to monitor temps with the on board diagnostic display so I'll just use that to check it.

 

Yes people have done it and reported that they had no problems. I chose to do the full swap.

 

I am curious about this as well. I just wouldn't do it on my car, lol. Like the
OP said, super easy to reinstall the mechanical fan and shroud. When I get my
330i back on the road, I will do the electric fan swap and get rid of the mechanical and aux fan. I had a 99 323i 5 speed which had just the electric fan.
One of the good things about the mechanical fan is the fan clutch is super cheap,
anywhere from 30 bucks and up.

 

Did the swap last week as my mechanical fan was just wind milling. Before I swapped I ran with just the AUX pusher fan and monitored with Torque pro. Temperatures stayed around 93 in ambient of around 55 in traffic. It would go to 93.+ and the fan came on, the thermostat opened maybe towards 97 and the temperature just dropped to mid 80s as the water went around the radiator and then went back towards 93. It just looked fairly normal and under control.
Removed both fans and put in a Hella, plus rad, expansion,hoses, idler pulleys, thermostat*2 and O rings and basically the temperature profile is the same.
I was going to run just on the AUX over the winter but decided that as it was 12 years old perhaps a new pusher was a better idea.
AM watching temperature like a good nerd and it still seems fine.
Car is 320i automatic I and was originally slightly concerned about tranny oil cooling, however, the oil gets cooled via a very small heat exchanger at the bottom of the radiator and I don't think that having the mechanical fan would make a whole lot of difference anyway.
As for the two fans, the blades will different profiles/pitch for a pusher and a puller. If you just put the pusher fan the other side of the radiator it will be blowing air forwards not drawing it through the radiator. Car will get hot.

 

That's correct that you could not mount the auxiliary fan on the other side and expect it to work. The components are all interchangeable, but being either a pusher/puller is dependent on being mounted in the correct shroud to get proper orientation. If I change anything, I'm leaning towards installing a second electric fan as a puller and wire it to a stand alone fan controller. That would still leave the stock auxiliary fan in place as a back up should the first fan fail. Some say to remove the auxiliary fan because it blocks airflow to the radiator, but it flows just fine for use with the mechanical fan so it can't be blocking much. The auxiliary fan shroud is actually pretty well designed with flaps that open up at speed to allow air to pass through to the radiator.

 

Yes, this works fine. Both my E46's are automatics and both have had the mechanical fans removed for several years. Also my E39 has it removed.

I didn't just do this as an insanely risky experiment either. I logged the coolant, engine oil, and ATF temps both before and after the mechanical fan removal and the graphs were the same.

I don't know where the idea came from that the puller fan is more efficient than the pusher fan. That doesn't make any sense at all. The fan is moving air from one side of the blades to the other, so it doesn't care if the load (radiator) is in front or behind it; it's the same load (resistance to air flow). The pusher and puller fans on these cars are identical except for the fan blades themselves, which are just slightly different.

 

Pushing vs. pulling makes no difference. This has been proven again and again in the PC overclocking world as well. If the same volume of air is going though the radiator than the same amount of heat is being dissipated.

BMW has to sell cars that can handle extremes from all over the world. For example: cars with automatics might need additional cooling when its 120 degrees outside in the Arizona sun sitting in bumper to bumper traffic.

YMMV if you delete your mechanical fan depending on the conditions you drive in. If you want to deviate from the stock setup do your homework and keep an eye on your temperatures when the car is trying its hardest to stay cool (super hot summer day sitting still in bumper to bumper traffic). If all your temps stay in spec you can probably delete your mechanical fan without any adverse effects.

 

computers don't move at 60 mph down the road.
the radiator is going to be more efficient with a puller fan than a pusher fan. more of the radiator is exposed for air to pass through during movement.

 

All I'll say is if I were to trust my e46 engine to a single fan unit (which I do on my two manuals) it certainly would NOT be an aftermarket Chinese fan (Behr / Hella) that has a history of failing, at least get the OE Bosch fan unit with a gen 2 module.

http://www.e46fanatics.com/forum/showpost.php?p=16713658&postcount=746

 

I'm running without the manual fan on my 99 e46 automatic, and the auxiliary fan has not come on yet. But my warm up time is faster and I get heat earlier in my commute. I'll monitor temps closely in July and August but expect to be fine with the mild climate in Oregon.

 

The puller fan is more efficient when stationary mainly because it does not sit in front of the air flow, most of its forced air will go through the radiators but some will be deflected. The puller fan is creating a low pressure area behind the radiator which will force air to be drawn through the radiator.
When you are moving the air will just get blown through and the fan shouldn't come on unless ambient is very high and you are hammering the auto box, so it is a good idea to remove any obstructions.
Most modern cars only have one fan and I believe later BMW autos only had the puller fan.
If you are going to leave the AUX fan and rewire it you probably ought to run a separately fused 12v supply to it as the fans draw lots of amps when running and it would not be wise to just piggy back off the current fan wires as they might get a little hot.
Also from what I have read having two similar fans doesn't always work as one fan can interfere with the other.
Assuming that you are basically just fitting the AUX fan in a puller shroud so the motor has gone through 180degrees then it will be blowing air through the radiator to the front of the car which won't cool it down. The fan blades may look similar but their pitch is reversed.

 

The puller fan is more efficient when stationary mainly because it does not sit in front of the air flow, most of its forced air will go through the radiators but some will be deflected. The puller fan is creating a low pressure area behind the radiator which will force air to be drawn through the radiator.
When you are moving the air will just get blown through and the fan shouldn't come on unless ambient is very high and you are hammering the auto box, so it is a good idea to remove any obstructions.
Most modern cars only have one fan and I believe later BMW autos only had the puller fan.
If you are going to leave the AUX fan and rewire it you probably ought to run a separately fused 12v supply to it as the fans draw lots of amps when running and it would not be wise to just piggy back off the current fan wires as they might get a little hot.
Also from what I have read having two similar fans doesn't always work as one fan can interfere with the other.
Assuming that you are basically just fitting the AUX fan in a puller shroud so the motor has gone through 180degrees then it will be blowing air through the radiator to the front of the car which won't cool it down. The fan blades may look similar but their pitch is reversed.

 

I'm not going to change anything with auxiliary fan,just leaving it as stock and letting it do its thing. I most likely won't need to add a puller fan, but if I did it would be wired separately with a stand alone controller, not wired into the aux fan circuit in any way. I don't see how having both an electric puller and the stock pusher could interfere with each other any more than the stock mechanical puller/ electric pusher combination does (or doesn't). As far as the aux fan bring an obstruction...,it's there from the factory already and doesn't seem to hinder air flow so there's no reason for it to become any more of an obstruction just because the mechanical fan is gone. It is a proven fact that pullers are more efficient than pushers in automotive uses, but that doesn't mean the pusher isn't capable of providing enough air flow to meet cooling requirements, which it seems it is based on the feedback from those who have tried it.

 

...It is a proven fact that pullers are more efficient than pushers in automotive uses...

Kindly show us where this fact is proven.

 

The shutoff speed multiplier (zero - cannot come on despite other input factors) for the fan is higher. In the example below from the e46 MSS54 DME the fan cannot be activated >140 Km/h. The second table is radiator outlet coolant temp. These are only two tables of the multiple input factors that determine the "final output" (all of the input tables/parameters are multiplied to determine the fan speed.)

Image courtesy of Terraphntm


Edit realized you said 60 mph = 100 km/h so your not far off. I always think in km/h

 

Pusher vs. Puller

There are arguments for both. The following excerpt from a Swedish University Masters thesis looked at Volvo options and offers some interesting considerations - although the net conclusion was that having the fan on the cool side is more efficient. (In the case of the E46 that would mean that leaving an auto electric fan in it's current location may actually be more efficient) Draw your own conclusions!

Here's an extract: (Page 31)


5.10 Pusher Fans vs. Puller Fans In the history of Volvo buses the fans have always been placed behind the heat exchangers, which could be called that the fans are placed in a pulling position. The reason for this is that he fans have been belt driven fan or hydraulic driven which makes it very complicated to go through the heat exchangers with the belt or oil pipes. It has also been a common solution shared by GTT. But for a cooling perspective it could be interesting to have the fans on the cooler side where the air has higher density giving a higher air mass flow for a certain fan speed.

When Volvo buses is more and more looking towards electrical fans it must be considered to have pushing fans since the motor in a pulling position is exposed to hot air heated by the radiator and charge air cooler. Electrical fans can also be easily mounted in front of the heat exchangers in a pushing position. One drawback is that the total cooling package gets thicker due to that the fans cannot be placed too close to the grille for safety demands and also that the fan shroud needs an extra frame to be mounted against the charge air cooler. One question rises through how the fan shroud should be designed for a pushing fan set from an aerodynamic point of view, which means that its optimum size might not be the same as for a pulling fan. In general, pulling air through the radiator works better than pushing it through it.

Since fans manufactures claim the same efficiency for both configurations, especially if the fan shroud is well designed. Otherwise, it can be said that pusher fans would be better. As there is always some leakage between the fan and the radiator (or charge air cooler), the fan does not just flow air through itself straight, since it spins causing turbulence. Centrifugal force throws air outward all along the fan as well, but the intake side is pretty much limited to the area of the fan. When the fan is in front of the remain cooling system, some air goes thrown out and never makes it through the radiator at all. Thus, if one compare total air moved with a pusher fan, less makes it through the radiator than the same fan as a puller.

The shroud effect is important when addressing this issue, especially regarding pusher fans. Other simulations comparing these two configurations were made to analyze the air flow velocity and it was concluded that there is not a big difference between them. This test was made in ambient temperature, which means that the density change, consequence of change in temperature, was not took into account. The mass flow is constant and will be the same wherever the fan is located. The density change is given by the temperature change in the hear exchangers. The pressure level in the heat exchanger will not be exactly the same for the two fan locations, but it is assumed the difference will not cause any change in density, as it is a fan and thus not a pressure difference in the system that causes density change.

Normally the temperature behind the heat exchangers is around 90 ***8451;, which entails to a correspondent 0,972 kg/mˆ3, compared to an air temperature of 20 ***8451; with a density of 1,204 kg/mˆ3. This increase of 24% in density could be translated in 24% increase in mass air flow. This means according to 20, that the heat dissipated by the cooling system could be improved the same percentage, if losses are neglected. Therefore, if the fans operate under this high temperature their lifetime is reduced and the conclusion is that in order to get as low power required as possible the fan shall be placed where the density is higher, i.e. at the cold side of the heat exchanger [27].

To read the whole paper:
http://kth.diva-portal.org/smash/get/diva2:763280/FULLTEXT01.pdf

 

Great post North! That study states exactly what I've seen in any other study, which is that a puller will move more air through the radiator than a pusher, which is what I'm referring to with regards to what has been proven in that cooling efficiency is typically measured by the amount of air moving through the radiator. This study brings up an interesting addition not usually mentioned though regarding air density. In any case, way back to my original post....I think the stock pusher fan appears to be up to the task of cooling the engine and taking the time to switch everything out to a puller may not be necessary. Certainly nothing wrong with doing that, but not something that has to be done either.

 

The benefit comes when it's time to swap out a failing fan unit. If you've configured it like a manual (puller) it can be swapped in under 5 minutes

Also part of the mechanical fan's function and the electric (in the case of the manual config) is to cool component parts at the front of your engine from direct blowing air. You will not have this benefit to the same extent.

You should also consider that with a factory buffered temp gauge any slight increase in coolant temp might be unnoticeable, since you are viewing only coolant temps (and are buffered to display "normal"). In reality however the absence of direct blowing air (especially at idle) to some components (i.e. the plastic t-stat housing, wp, hose connectors etc.) and the increased temperature and lack of cooling air might accelerate failure.

 

Hmm. This is interesting. When I get home I'll remove the manual fan and see what happens. As it is, I already have the front kidneys blocked off because it's so cold the car can't heat up in a reasonable time. So I'll report back in a week with my findings. Granted, is been -10 to about 20 F so I can't imagine it will be a good test.

 

Well good news, after a few weeks of testing it works great. Anything under 37f that is. Never goes over 204.8 except one day it was 40 out and I was driving in the city, it got up to 210 so 37 seems to be the max temp you can drive without your manual fan on. Few things I've noticed is that, it's much quieter, noticeable Increase in acceleration, 2mpg increase in mileage. That was a average after 4 tanks

 

Interesting. I've driven mine in up to 60 degree temps now with no problem. I've been monitoring the coolant temps via the on board diagnostics, not the dummy gauge, and the hottest it will allow is 90 Celsius at which point the fan kicks on and temp drops to around 84 in less than a minute. Are your front kidneys still blocked off?

 

That's interesting. No I did remove the blocks I had in the kidneys. My aux fan doesn't seem to like turning on. I don't think it's ever on if I don't have the AC on. I do have an XI, but don't think there any different