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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 08-28-2013, 06:29 AM
small_525 small_525 is offline
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New Alt

Not wanting to steel a thread so started a new.
New alt on eBay for I6
http://www.ebay.com/itm/NEW-Genuine-...-/141035603526

Looking at the picture it looks like there is a screen/filter on that elbow on the rear cap. I don't recall seeing one on my old or rebuilt one so I put scotchbrite in the lower grill to keep the leaves out. I wonder of that isn't a nicer option (cleaner looking)? Realoem doesn't detail of the replacement cap has that there or not.

Anyone have that as OEM? Got pictures. Any idea if something could be fashioned to work like that? I'd thought about it but wasn't certain how or what to do. Another DIY option?
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  #2  
Old 08-28-2013, 07:04 AM
cn90 cn90 is offline
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Actually that cap is useless. Remove it.
That cap is a response to issues with leaves collecting in the alternator. Another dumb solution to a problem.
So instead of leaves collecting inside the alternator, it collects at that rubber cap!!!


Also, don't attach the factory air duct, while great in theory, in reality it is not. It collects leaves, debris brought in from the bumper intake area.
Unless you install a screen at the bumper (I posted some photo of that in another thread), get rid of the factory air duct.

To summarize it:
- Remove factory air duct.
- If you buy this new Bosch alt, remove the rubber screen.

Many many cars don't have any of these ducts and do just fine. It is over-engineering without real-world feedback.
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  #3  
Old 08-28-2013, 08:13 AM
crazy4trains crazy4trains is offline
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Since this discussion has come up I will add my 2 cents. I put a new Autozone alternator on my 2002 530i about one year ago. After coming back from vacation this year my car would not start. I charged the battery and went on my merry way. I decided to check the OBC and noticed that at times the alternator was only putting out 12.8 volts at idle. The condition got worse during the hottest days of this past summer. I had to take a 4 hour (round trip) and charged the battery prior to leaving to ensure I was good to go. On the way back I stopped to eat lunch. The car was sluggish but would start. There happened to be an Autozone right there so I pulled in and asked if he could check my alternator on the car. He said yes and proceeded to get to work. Result was that my voltage regulator was bad. Note that it was 95 degrees on this day. I was able to make the drive home while watching the OBC register about 13.2 volts. Not where I wanted it but enough to get me home.

Once home I removed the alternator and took it to my local Autozone for replacement. When they checked it on their testing machine the alternator tested OK. I gave them my sob story and ultimately they replaced it. One thing to note is that when I pulled the alternator off, the duct had come apart. This thing probably does need a good source of cool air. I added a piece of gutter guard at the vent in the bumper to screen leaves etc. when I bought the car, so leaf debris etc. was not the issue on the replacement.
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Last edited by crazy4trains; 08-28-2013 at 08:23 AM.
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  #4  
Old 08-28-2013, 08:19 AM
small_525 small_525 is offline
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cn90 your gutter guard and my scotch-brite in effect do what this rubber piece is doing. SO I don't understand how yours or my method is better, other then it makes it easy to clean when washing the car. Granted most people won't notice your gutter guard remedy, but if its totally concealed with this rubber piece and its cleaned out annually then I'd think it "better" . If you still have yours I'll email you my address and you can send it my way.
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  #5  
Old 08-28-2013, 08:30 AM
cn90 cn90 is offline
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Actually I posted the alt so people can buy it new.
I don't have the rubber piece at home, but from looking at it, it is basically useless.

I have quite a few cars at home, and none of them has this useless rubber screen.
Just install it minus all the air duct, rubber screen and people will do just fine.
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  #6  
Old 08-28-2013, 09:52 AM
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bluebee bluebee is offline
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For the record, I'll cross reference this to the canonical thread, found by typing either /alternator or /leaves in the bestlinks:
- How to prevent leaves in your alternator air-intake duct (1) (2)
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Note: Your mission, should you decide to accept it, is to add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need, in seconds!

Last edited by bluebee; 08-28-2013 at 09:55 AM.
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  #7  
Old 08-29-2013, 09:55 AM
small_525 small_525 is offline
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cn90 telling folks not to at least install the duct. Your gutter guard is more useful then this rubber screen?? I mean there had to be a point to having the engineers design that beyond "make work" yes there is a bunch of overdoing in these cars but look at the alt. Most Alternators come equipped with a sizable external fan, these have a pretty small one on the inside. What is to keep them cool? Heat kills electronics, hell the leaves blocking the air and then insulating the alt contributed to the death of the alt. This is the stuff on the back that is being cooled by the ram air coming in. Some of these over engineered cars come with a water cooled. Yes the fail too.
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  #8  
Old 08-29-2013, 10:04 AM
cn90 cn90 is offline
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My 1998 Volvo S70 with 150K+ miles still has the OEM Bosch alternator!
Volvo, Honda, Toyota etc. do NOT use air duct.

Air duct is nice in theory but in reality, it backfires when leaves debris get in.

Look, people in this forum replace their alternators at 50K-100K, thanks to the dumb engineers.
Get rid of the duct and move on.

Nothing lasts forever, if you can get 150K out of an alt, it is good.
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  #9  
Old 08-29-2013, 11:30 AM
small_525 small_525 is offline
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256,000 miles on the e34 with the original alternator w/a air duct so I win. The leaves potentially did screw mine at 65,000 on this e39 but I don't have the rubber screen. What was the point of you adding the gutter guard in that diy? I agree the rubber screen will collect leaves and block air flow so it would need to be cleaned once in a while. Taking yours off is cool I just don't think I'd being telling others its the way to go. Tell them to check and clean would be more appropriate.

Last edited by small_525; 08-29-2013 at 11:32 AM.
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  #10  
Old 08-29-2013, 11:43 AM
crazy4trains crazy4trains is offline
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I added the gutter guard to the front bumper vent on my 02 530i. Why? Because I threw the perforated in-line screen in the trash. I can see, and therefore clean, the gutter guard on the front bumper when I wash the car. I would clean the in-line vent in, well....never. Makes lots of sense to me.
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  #11  
Old 08-29-2013, 11:46 AM
cn90 cn90 is offline
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small_525,

My opinion is my opinion. I don't tell people what to do.
I tell people what I'd do personally.

People are all adults so they make their own judgment.

Sometimes we give BMW engineers too much credit. Yes, 90% of the time, they are good but 10% of the time, they screw it up. This is one of them.

Now "Tell them to check and clean would be more appropriate"...
I agree with this statement but checking this is not easy, one has to bend down, remove the air duct, inspect etc. Most people are busy, so I suggest to them the easy solution.
Get rid of the air duct, put it in the weekly recycling bin, set it at the curbside on trash day, problem solved!

Go and look at Volvo, Honda, Toyota etc. alternator, then people would say..."look ma no air duct".
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