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  #1  
Old 01-13-2006, 09:17 PM
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bent alternator bracket adj bolt-123

My alternator bracket adjustment bolt and the bracket piece that holds the nut has bent for the second time since I've owned this car. Either I'm doing something wrong or this is poorly designed. Does anybody else have this problem?

As I tighten the fan belt with the adjusment nut the force pulls the weak part of the bracket that the nut is mounted in away from the bracket, also bending the bolt in the process. As soon as the fan belt starts to get tight I see this bend happening. It doesn't seem to me that I'm overtightening but maybe I am. The fan belt isn't that tight! I've loosened the other bracket mounting bolts so I'm not working against them. What's the solution here???

Thanks!

Randy
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  #2  
Old 01-13-2006, 09:34 PM
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The bolt on the 616 in my 307d was bent. I had to call road service in France since the belt was slipping badly and I couldn't tighten it. They removed the bracket, hammered it straight and put it back in. I don't like the design. There is a bracket style that does not utilize the bolt. Go to a junkyard and see if you can find one.
I was curious as to how the bolt got bent to begin with. Your observations explain it.
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  #3  
Old 01-13-2006, 09:46 PM
t walgamuth's Avatar
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yeah

they are kindof easy to bend... especially if you dont loosten all the other bolts such as the bottom pivot bolt. i bet yours is binding somewhere you havent as yet discovered. i think they are an excellent design, miles ahead of the pos on the 115 alternators. they are relatively fragile though.

tom w
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  #4  
Old 01-13-2006, 11:23 PM
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Tom,

So do you think the bottom bolt actually holds it in position? I wondered about that...





Randy
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  #5  
Old 01-14-2006, 05:29 AM
t walgamuth's Avatar
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oh yeah

if you dont loosten that bolt it wont adjust for hooey! i have tried. bent bracket is the result.

i wondered.

it seems like a lot of bother to loosten that one on the bottom but it needs to be done.

good luck

tom w
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual. It still needs upholstery redone...I also have a 427 Cobra replica with an aluminum chassis.
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  #6  
Old 01-14-2006, 02:06 PM
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OK. Well that's not it!

I've loosened all the bolts. There is no restriction to the alternator moving . But when I tighten the adjustment bolt the "prong" or "tab" that holds the adjustment nut STILL bends outward. It is such a weak configuration that the pressure or resistance of the fan belt causes the adjusment bolt mounting tab to bend outward.

Baffled...




Randy
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  #7  
Old 01-14-2006, 02:23 PM
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I had to fix the same thing on my mothers 240. The actual bracket snapped. I think what you are supposed to do is use the adjustment bolt to get the belt tight and then crank down all of the other bolts, and then back off on the adjustment bolt. The bolt is to flimsy to always be carrying the load of keeping the belt tight. I have had no trouble with it since then.
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  #8  
Old 01-14-2006, 04:24 PM
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"Go to a junkyard and see if you can find one."

Thats the way I fixed mine, no more problem, just place a bar in back of the atl, apply a little pressure and tighten the 17mm nut.
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  #9  
Old 01-14-2006, 04:36 PM
Brandon314159
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BTW that bracket probably USED to do the job (my 300SD does just fine...the bolt is bent yes but it still works).

The problem is...once it bends...it will never be the same strength. You could weld a helper piece and re-engineer the bracket to suit your needs if you wanted.

Your alternator should flop around looosely if everything is loose for adjustment. If not...you still got somethin binding.
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  #10  
Old 01-14-2006, 08:06 PM
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Snap it off...

I bent mine and thought I would have to buy a replacement...I called my local indy mech and he said every bent one he sees they just snap it off and use a crowbar to pull tight the alt and then tighten the bolt...I did that 3k miles ago and she is running great! Much easier for replacement of the alt as well...
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  #11  
Old 01-14-2006, 09:49 PM
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Thumbs up

Mine became bent on the SD a while back. I wish that motor had a single belt like my L.
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  #12  
Old 01-14-2006, 10:37 PM
Brandon314159
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Quote:
Originally Posted by Hit Man X
I wish that motor had a single belt like my L.
...until it fails
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  #13  
Old 01-14-2006, 11:19 PM
t walgamuth's Avatar
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yeah

the double belts are the berries.

imho

tom w
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual. It still needs upholstery redone...I also have a 427 Cobra replica with an aluminum chassis.
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  #14  
Old 01-15-2006, 12:14 AM
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I'm going to take the reverse tack on this.

I recently bought a new bolt for the SD because it never had one (presumably bent and broken by the PO???).

It worked perfectly for me. I had to bend one of the tabs on the bracket to get the bolt installed and then bend it back in place.

However, tightening it was as designed. The belts easily tensioned to the level necessary and the bolt did not bend.

Why??

I believe that some of you may be overtightening the belts. I can move the belts 1/2" in the center when I'm done. The wrap on the alternator, from two belts, is more than sufficient for the required torque.

In fact, I recently proved this when the alt light would intermittently come on and then go out. It was a rainy night and I was not about to stop and bother with it.

The next day, I find that the belts have nearly 1" of play in the middle.

They had stretched a bit during the first 1000 miles after installation and were slipping, only slightly, when they got some splash from the road.

So, I loosened the three nuts, tightened the adjustment bolt so that they returned to approx. 1/2" in the middle, and retightened the nuts.

No bending of the bracket and no slipping of the belts.

YMMV

Last edited by Brian Carlton; 01-15-2006 at 11:12 AM.
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  #15  
Old 01-15-2006, 12:43 AM
Brandon314159
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Quote:
Originally Posted by Brian Carlton
I'm going to take the reverse tack on this.

I recently bought a new bolt for the SD because it never had one (presumably bent and broken by the PO???).

It worked perfectly for me. I had to bend one of the tabs on the bracket to get the bolt installed and then bend it back in place.

However, tightening it was as designed. The belts easily tensioned to the level necessary and the bolt did not bend.
My exact situation...my bolt was bent from the PO but I have never bent it thus far...

Owning an aircooled VW makes you learn that belt tension is IMPORTANT and overtightning is BAD.

Espically when you risk (in the mercedes) damage to the harmonic balancer and all that jazz.
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