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Water Cooled Alternator/Generator (1999-540i)

Discussion in 'E39 (1997-2003)' started by mswalk01, Jul 18, 2011.

    mswalk01 guest

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    I have a 1999 540i and I'm wondering if anyone has step by step instructions for removing and installing a new water cooled alternator.

    This past weekend my wife and I were returning home from a week long vacation when I saw the red battery light come on in the dash. Being that we were between 135 and 145 miles from home I couldn't just have it towed. After a thorough inspection and a battery and alternator test I decided to have my battery recharged to full capacity, buy a fully charged back up and hit the road again this time with no AC or radio. We drove till it started getting dark, crashed at a hotel for one more night then got up in the morning to finish the trip. Now that we are home we have her 2002 325i and my 1986 944 to get around in and I've started talking to people about having it changed. I am having a hard time paying $450.00 for a reman alt, then another $400.00 to install it when I know that I can do it myself with the proper instructions. I don't have a "Bentley Brick" yet and so I'm reaching out to all of you. Thanks in advance as this is one of the first posts to a forum that I have ever made.
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    MGarrison

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    Well, welcome to the world of

    Well, welcome to the world of interwebz forumz and what not. If you want to swap alternators, the Bentley manual should outline the remove/install procedures. I say should, as I neither have experience with E39's, or their Bentley manual. I wasn't aware that the alternators were water cooled, but if that's the stock setup, then Bentley procedures should cover that. I've found the Bentley manuals for my cars (E30, E34) to be very good, but not surprisingly, not always covering every detail; sometimes you have to figure out an intermediate step that isn't detailed enough. If you're mechanically inclined, & have the time & the tools, it's probably a do-able d-i-y job, unless a specialty BMW-only tool is necessary. Otherwise, it's likely mostly a matter of following directions and removing and replacing parts - relatively straightforward as long as you keep track of things, and put everything back together correctly. Be careful to torque bolts to spec when re-installing, or at least to not over-tighten; breaking things will cause unnecessary nuisance.

    If you're talking about wanting to install a water-cooled alternator when the oem unit wasn't water-cooled, then you're getting into a different scope of project. Figuring out how to adapt something that isn't oem obviously isn't going to be detailed in the Bentley manual.

    Those V8's are known to have fan blades fail (wiping out cooling hoses and damaging the hood), the radiator necks to give up the ghost (be wary of failure on an original radiator at any mileage above 100k), the expansion tanks failing (causing cooling system problems - just what anyone wants, a cooling system contaminated with bits of plastic), and the original water-pump plastic impellers failing and circulating through the cooling system.

    If you're above 100k and are somewhat risk-averse, you might want to consider replacing those items, or examining them carefully. The transmission went out on my mom's '97 740il last year (slightly above 100k), so if you have an automatic, it might be worthwhile to consider whatever can be serviced with the transmission (I think there may be some seals that can be changed, and draining trans fluid and refilling with fresh are possibilities - you may have to check some of the other BMW-specific forums for more details, as the club just re-vamped these, and we don't have much on record, or folks on hand, yet). I had the mechanic go to install a new fan blade, and the radiator neck cracked just from being bumped by his hand, so we went with a new radiator and expansion tank too. Dodged a bullet on the water pump, it made noise last fall, and thankfully the impeller didn't fail, so it was able to be replaced before failing completely.

    Point being - if you have to get into any of the cooling system to do your alternator swap, and you haven't already addressed the cooling system issues that seem to be pretty common with those motors, and you're on original components or around that mileage, and you plan on wanting the car to run reliably well into the forseeable future, it might be easier to do some of that while in there for the alternator, particularly if you have to drain the coolant system anyway 'coz the alternator's part of the coolant routing.

    YMMV (your mileage may vary) - I don't know that these problems are universal, but, they do seem to be noted by owners, in multiple instances. If you want peace-of-mind, swapping things out pre-emptively is likely both less inconvenient and expensive than having something cause a problem unexpectedly.

    Lastly, the internet is-what-it-is; although good advice is to be had, it pays to do your own research. Since the 'net is free, sometimes ya get what you pay for. I wouldn't suggest making spending and purchase decisions just based on a total stranger's comment(s) off the internet - a little research can go a long way.

    Not to plug other forums, but they're also a good source for info -

    http://www.bimmerfest.com, http://www.bimmerforums.com, http://bimmer.roadfly.com/bmw/forums/e39/ , http://www.bimmerboard.com/forums/e39/ , http://www.e38.org/e39/

    Bavauto.com and pelicanparts.com also have various types of tech info/articles. There are others, google is always handy for digging up info, etc. If you shop around the 'net, Roundel advertising vendors, and dealers that offer a club-member discount, you may find an oem alternator less than BMW full retail. Bavauto.com, for one, offers price matching.

    Zionsville autosport (no, I have no affiliation) has some pricey but very nicely done radiators and water pumps - http://www.zionsvilleautosport.com/store/screen/ctgy/store_code/6134/category_code/CCSE39.htm, should those be of interest.

    Sorry not to have specifics on what you need to do. I assume it would be along the lines of removing the serpentine belt (perhaps you have to pull the radiator for that?), swapping the alternator out, getting the belt back on (might be advisable to use a new belt, and/or belt tensioner), and filling and bleeding the coolant system. That's only my guess though, and doesn't help with the specifics. Maybe somebody who's done it will kick in, but until these forums get re-vamped to be more user-friendly, I don't know that we have too many on-hand to advise you in detail. You should be able to get the Bentley manual from Bavauto.com, although you ought to be able to google up any number of sources for that.

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