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  #1  
Old 10-03-2015, 10:43 PM
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Alternator bracket fix?

1981 240D

So, I know this is a perennial problem, but I have a mangled alternator bracket. The previous owner seems to have lost the spacer, which resulted in a bent bracket and a mangled adjuster thread. I bought a new spacer, but there was no way I could bend the bracket so that the spacer would fit and when I finally measured every thing, it turns out that the alternator+spacer = .010" longer than the bracket appears to have ever been. Anyway, I ground it down a touch so that it would fit, but there is just no way around the fact that the $80 adjuster bolt is mangled beyond use, so I just put it back together without the nut installed so that I can adjust it like, well like every functional alternator bracket I have encountered on every other car I've ever owned. I honestly don't know why Mercedes had to inflict such a marginal piece of engineering on us, when most of the rest of the car is so well thought out, but I just can't stomach the idea of spending $250 on a new bracket that will be every bit as marginal as the one I already have. So my question is, what are my other options for an alternator bracket? I know that there is the star design, but I don't know what the level of compatibility is with my block/alternator/etc. How many parts do I have to replace? Also, I've heard that people don't like the star design either. Has anyone made their own bracket? I'm tempted to think that if I can put a large enough hole in the right place on the existing bracket, I could get a pry bar in the right space to put the correct amount of tension on the belt without needing the adjuster.
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  #2  
Old 10-03-2015, 11:17 PM
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I am not sure what alternator bracket that you have. If you have the type that has a rod inserted into the head of a Bolt the you can fix it cheaply by getting a longer Boilt and an Eye Bolt as pictured. However, instead of double nutting the Bolt you can use a self locking Nut.

What often ruins the originals are the tensioner screw rusted to the skinny rod or someone forgets to loosen the 17mm Nut on th long blot that the skinny rod goes through.
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Alternator bracket fix?-alternator-tensioner-bolt-repair-eye-bolt.jpg   Alternator bracket fix?-alternator-bracket-tensioner-bolt.jpg  
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  #3  
Old 10-03-2015, 11:26 PM
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Yes, that's the type I have. I like your idea, I wish I had thought it up myself. It looks way less sketchy than the factory solution.
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  #4  
Old 10-03-2015, 11:29 PM
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Quote:
Originally Posted by SWjames View Post
Yes, that's the type I have. I like your idea, I wish I had thought it up myself. It looks way less sketchy than the factory solution.
I don't know who to give credit to but it was not my idea. I copied the pic for my Notes and rememberd it.
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  #5  
Old 10-04-2015, 03:16 AM
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i've done the eye bolt fix and it works flawlessly.
i used a coupling nut on the end to make it similar to the factory



i've used the star bolt too, i actually think it works better than the later version so long as there arent any teeth missing from the star. but even then, a new star bolt is like $20 from mercedes
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  #6  
Old 10-04-2015, 01:27 PM
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another alternative would be to buy & use an alternator adjustment hook (see photo). (Bosch alt & hook in photo) I think I paid $7 for the hook. Uses a 1/2" drive breaker bar or ratchet as the lever.

BTW - I agree that MB really dropped the ball when they designed & implemented their adjustable bracket.
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  #7  
Old 10-04-2015, 07:20 PM
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An alternator adjuster hook? I need one for sure. However, the eyebolt worked perfectly and cost me only $5 and that only because I bought a stainless M10 bolt.

I want to take a picture of the alternator on my 6.2l detroit diesel and send it to Mercedes and tell them, "you want to know how to install an alternator? Look under the hood of pretty much any American truck, ever!" Mine even has a convenient hole in the bracket for the insertion of a pry bar for tensioning the belt. I guess the use of a pry bar is just too much for the feint-hearted MB engineers :-)
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  #8  
Old 10-04-2015, 08:08 PM
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I think I found the hook on a Lisle Tool display in the local indie parts store. The original was marketed towards folks working on GMs before they put the hole in the bracket...dates back to the 10SI alternator.

BTW I have an old MB tool kit that came with a pry bar, about 8" long. I've used it many times to snug up a V belt alternator.
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  #9  
Old 10-06-2015, 12:19 PM
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Weld a tab...

...to prevent the housing from deforming. Mercedes engineers plain forgot it.
If a tab is welded across the top of the right end arrangement to prevent it from deforming, it should solve the problem by keeping the adjusting nut straight, and preventing the bolt from deforming. It should take three good tack welds. TIG would look better.
There isn't a lot to prevent deforming with the original design. From what I observed, the arrangement, although appearing to be sturdy enough, seems to have metal that serves no purpose, with the end result being only as strong as one that had only one tab.
Once this is welded, the weak link in the assembly would be the adjuster threads. or perhaps the fused bolt joint. Don't go using a cheater.
I have a '79 240D with a shiny new bracket. So far, still charging and no squealing. But that may change.

snapped_bolt
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'81 240D For now, a good place to borrow new parts
'80 300TD Probably will be put back into service!
'79 240D BACK IN SERVICE SINCE 09/16; limited use, oil leak. Guide pin r/sealed/replaced. Still a leak. Front crank seal....
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  #10  
Old 10-06-2015, 03:19 PM
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I don't know why so many people have issues with mercedes tensionor design.....

I love it, compare to having to call a buddy to tighten the bolts why you put all your weight on a breaker bar to hold the alternator back.....just to find out there is to much tension on the belt....

All you have to do is loosen up the bolts, and use the tensioner bolt....then tighten up the bolts.....I am not understanding the complicatedness everyone seems to have...

The issue with destroying the tensioner on the alternator and power steering pump is because idiots try to use the tensioner with out loosening the bolts...

Remember these belts are not suppose to be so tight you can play a tune on them...

I am running the original brackets on both the 82 and 78....the tensioner are rusty, been re straighten and everything in between....They are still holding and charging....

I mean if mercedes engineers made so many horrible design mistakes, then why are/where so many other manufacturers coping their designs....
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  #11  
Old 10-06-2015, 04:24 PM
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Mercedes engineering

Yes, I do

of course

that's why I drive one when I am not working on it. But the arrangement is just different than the typical domestic, at least for many years worth of vehicle applications. So, yes, many will use a shovel handle to pry on the
alternator as the tension bolt is adjusted. Made sense for the domestics because it works.
Do the same thing on the Mercedes and the results are not quite the same, so many show the outcome of domestic repair on a Mercedes design- or, a Haynes repair on an FSM fix.

Bend, strip, snap.

A steel tab would still prevent deformation. After 3 decades of PO's, most have gotten the works in fix attempts.


Cheers!

snapped_bolt
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'81 240D For now, a good place to borrow new parts
'80 300TD Probably will be put back into service!
'79 240D BACK IN SERVICE SINCE 09/16; limited use, oil leak. Guide pin r/sealed/replaced. Still a leak. Front crank seal....
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  #12  
Old 10-06-2015, 04:57 PM
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I think the point has been missed. The car was made to be worked on by Mercedes Trained Mechanics. For the DIY types seeing something different should send you looking for a source of accurate information on it; doing things blindly base on experience on other Cars can get you into trouble.

The power steering adjusment bolt is a case in point. On mine a Hose nearly competetly covers over the adjustment bolt and even harder to see wiith it full of gunk around the Bolt. The Manual showed me where to look for it.
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Last edited by Diesel911; 10-06-2015 at 09:33 PM.
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  #13  
Old 10-06-2015, 05:07 PM
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Exclamation

What he said ! .

I killed the bracket on my first 'Benz , never had any issues after .
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-Nate
1982 240D creampuff 367,000 miles (SWMBO's)
1978 300CD back from the dead SOLD
1980 300CD 90K Miles ICE COLD AC ~ SOLD
1984 300CD KEEPER ! 420,XXX miles
1984 Euro 300TD Fully optioned
1974 350SLC 4 speed stickshift SOLD & missed
Krazy Kommie Ural Motos (3)
BMW Motos /5's SOLD
Vintage Air Cooled VW's all gone =8-(
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  #14  
Old 10-06-2015, 09:35 PM
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Well I have to say that some people have had the adjusting nut so badly rust to the skinny threaded rod that it breaks the rod when you turn the nut. Lots of things to blame on former owners.
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  #15  
Old 10-07-2015, 12:27 AM
Precision Somethingist.
 
Join Date: Jul 2011
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Former owners...

It just made more sense to me to blame former owners. Otherwise, I would have only innocent bystanders, or Mercedes Trained Mechanics to blame?


Cheers,


snapped_bolt
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'81 240D For now, a good place to borrow new parts
'80 300TD Probably will be put back into service!
'79 240D BACK IN SERVICE SINCE 09/16; limited use, oil leak. Guide pin r/sealed/replaced. Still a leak. Front crank seal....
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