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2003 325Ci Convertible
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Discussion Starter #1
Hey guys, I wanted to put this out there in case anyone else has a similar issue.

Ever since I got my car (2003 e46 325Ci Cabrio) I've been suffering from poor fuel economy but just thought that it was 'normal' since I drive the car like a bat out of hell pretty much all the time. Recently I replaced the vanos seals and, in addition to the much better low-end torque, my MPG went from 17.3 mpg to 20.1 mpg (according to the OBD). Yours might be better if you don't drive the car as hard as I do...

I was kind of shocked since the seals must have been bad at 49k when I bought the car - others have suggested that the seals are bad after only 20k of driving...

I'm probably going to try an electric fan conversion in the future, and if that helps I'll put that here as well.

TLDR; Replaced Vanos Seals, gained 3mpg (17.3 --> 20.1)
 

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E30M3 Race F10 535 R1150Rt M Coupe
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The fan conversion will help some, albeit a properly operating fan clutch only comes on (creates engine drag) only in city traffic and only when the radiator is hot.

The upshot of it is that it requires no electronics to operate. I've read many posts about failing electrical issues and temp sensors. Being an ex racer, I'm a huge fan of simplicity and redundancy.
 

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2003 325Ci Convertible
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Discussion Starter #3
I really just want to get rid of it because (1) its a pain to remove when you're doing work on the car, (2) it pretty darn loud, and (3) I'm hoping that the engine might warm up a little faster in the winter months

The potential mpg and power 'gains', if any, are just a bonus. I agree that the mechanical fan if probably more reliable, but it's just not worth it to me...
 

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E30M3 Race F10 535 R1150Rt M Coupe
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I completely understand. Just wanted to give insight to the complete picture.
There's a lot of misinformation here about how the two different systems (puller fan/fan clutch) operate.

Been working on getting it corrected in the conversations for a while.
 

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2003 325Ci Convertible
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Discussion Starter #5
I get it - someone suggested to me that the mechanical fan runs 24/7... I ignored them... 🙃
 

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E46 '04 330Ci convertible 745K km
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I get it - someone suggested to me that the mechanical fan runs 24/7... I ignored them... 🙃
Mechanical fan visually run always, yes, but it engages for work ( therefore creates drag) only on certain conditions, as Mr. Car just said.
I doubt you will really see the difference in HP or MPG. But it guarantees you are safe in case of electrical fails - and it not always failing dead - and temp will rize but you might not notice because of temp gauge algorithm. Mechanical fan also adds cooling to ATF heat exchanger and moves more air under a bonnet than electrical one.
If MPG is a concern, make sure your MAF and O sensors are in right order. Driving habits affect economy much more than a fan clutch)
 

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Having just tried to work on the automatic parts car, I would delete it, too-

the manuals with no engine fan are SO MUCH EASIER to get to.

But then, we live in a cooler climate.

Thanks for the additional push to do the VANOS- I keep putting it off,
because it's one of those fussy jobs I hate.

t
 

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E39 E90 E46 F10
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I'd do it sooner than later for sure. When the o-rings collapse the piston starts scraping against the bottom of the chamber (gravity side) as it moves in and out. Picture below is from my convertible at 12 years and 59k miles. Not enough to feel on my fingernail yet but I'm sure at some point you start doing real damage.

908884
 

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Hmmm. You're saying the mechanical fan can't cool the engine sufficiently?

t
 

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E46 '04 330Ci convertible 745K km
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Aux fan meant to help main one. It has a certain algorithm of engaging depending on ambient temp, coolant temp, engine temp, condenser pressure and vehicle speed. It will not save engine in case clutch fails. But without aux fan main one could be insufficient too.
 

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E30M3 Race F10 535 R1150Rt M Coupe
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Not again...
The mechanical fan is the primary. If your car has an electric fan in FRONT of the radiator, it's an auxiliary fan.

What's the most demanding cooling system in the E46 range? The M3. What fan does that car have? Mechanical fan and fan clutch.
Why? Because the electric does not pull enough CFM.
 

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2003 325Ci Convertible
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Discussion Starter #14
@cvx5832 Holy smokes... my piston housing had no such scoring on it at all.. Done at 104k on M54B25.

@BaliDawg Are you saying that you would prefer an electric fan over mechanical? Also, why can't I just leave the aux fan in - my car already has a connector for an electric fan that's unused.

@TobyB Honestly it sucks. That stupid fan makes working on everything hard. The hardest part of the VANOS - Removing that stupid fan... much rather just side an electric up and out...
 

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Discussion Starter #15
@Anticdubai I've been thinking about O2 sensors as well... but they are $$$ and honestly I'm not too bothered by the MPG - If I was I wouldn't drive it hard all the time. I was just pleasantly surprised at the effect on mpg - especially since I've been driving it even harder, if anything, since replacing the seals
 

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Oddly, my manual transmission 330 has no mechanical fan. I don't miss it. Nor does it overheat.

I'm trying to get the parts car engine running well, as it's a swap candidate for another car, and I'd
rather eliminate as many variables BEFORE I start swapping.

t
is wuss
 

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E46 '04 330Ci convertible 745K km
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@TobyB Honestly it sucks. That stupid fan makes working on everything hard. The hardest part of the VANOS - Removing that stupid fan... much rather just side an electric up and out...
[/QUOTE]
removing fan could be hard if you have no proper tools, but once you did it, it is easy every time you need to perform it again. takes 5 min flat. just no need to tight it too much, it isn't crankshaft pulley bold. I use 32 wrench and all I need is one-two hits by a hammer to unscrew/tight. Never used a holder tool.
 

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E30M3 Race F10 535 R1150Rt M Coupe
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With the two proper tools, the fan comes right off. Most overtighten the shit out of it fearing it will fall off. It's reverse thread. Self tightening. Then when too tight it gets a bad rap. Mostly diy or technician induced.

Manual transmission cars had no fan clutch.
Automatic transmission cars imposed a heavier load into the engine cooling system because of the increased load of cooling the ATF oil.
What did BMW do? Install a mechanical fan to take care of the increased load/BTU.
 

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E46 '04 330Ci convertible 745K km
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Never understood the reason to replace clutch fan with electric one. Noise reduction? - it is questionable. Power increase - I doubt it is any significant. Easier access for engine works? - you still need to remove shroud to get easy access. Protecting bonnet and radiator from broken fan blades in case clutch stuck? - seriously?
Trading extra level of safety for any of the above?
 

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E39 E90 E46 F10
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I did and I’m happy with my choice. Temp sensors in and around the engine verify its success and repeated across more than a few members.

This is another one of those spec-anal debates like coolant, oil and transmission fluid but the proof is in the pudding. At this point we can agree to disagree.
 
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