I had a broken tension bolt and made a new one. I bought the right bolt and nut, then I drilled a 5/16? hole in one of the flats of the bolt, sawed the head off of a 5/16 bolt and welded it in place, i used a 5/16 threaded rod connector and a washer for the tensoin bracket. worked well for me . I will get a picture if you like.

No need to bud, I have a pretty good idea of how it looks.

What i'm going to do is find a long bolt similar to the original, but have it have a hole on the end. I'll put a locking nut on the belt side and use an open Eye hook. I'll a washer and two locking and adjustment bolts for the tension adjustment.

It's christmas so none of the hardware stores are open. I'll do it tomorrow.

Merry Christmas everyone!

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-Typos courtesy of my mobile phone.

Hi
That tensioner bolt is such a poor design and pain that I decided to just get rid of it.

I replaced the "L" bolt with just a regular bolt and used a pry bar to tighten the belt. Then I tightened all the bolts to lock the adjustment in place

It has worked fine so far.

Of course mine is just a daily driver so I'm not too concerned with having everything pure MB

Joseph

After disassembling my bent and mangled tensioner and straightened it so it's back to 100% functional, I realized that some previous "wrench" adjusted it without loosening the lock nut first and that's why it was bent and mangled, not because it's a bad design

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

There are a few threads about worn out alternator bolts and nuts. On my car the PO lost the washer and wore grooves into the bracket and nut. I had to remove the bracket and hammer it flat and file off the burrs to make the action smooth. There are pics of other bolts where they clearly weren't used correctly:

Getting Alternator Off?

Alternator adjusting bolt

There appear to be a few types of brackets, bolts and styles. The parts blow-up shows a threaded rod w/ welded nut (#203) or the 90-degree (#206). There are also at least 3 and maybe 4 styles of brackets with/without welded nuts.

http://www.peachparts.com/shopforum/attachments/diesel-discussion/85147d1285590241-getting-alternator-off-alt-exploded-view-other-bracket.jpg

Some pics of the "eyebolt" fix are here: Alternator adjustment bolt fix

The pics show a wood screw thread (I think for illustration only) but use a machine screw thread. This fix seems to be an expedient substitute for the #203 style tensioner - assuming the bolt that goes through the bracket is long enough. Maybe needs an extra quarter-inch?

Thanks for the links yak. I had a bear finding them in the search that I bookmarked it. Certainly will help other poor saps like myself find them in the future

__________________
-Typos courtesy of my mobile phone.

I used a 3/8 breaker bar with a 16" pipe for extra leverage and a 17 mm socket to break free the bolts then used a ratchet.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Sorry to revive an old thread, but I got around to taking picture of the new tension bolt. The fix is incredibly strong. Germans like to make everything unnecessarily complicated

I've attached it below for reference to any other poor souls who cursed as much as me. Total cost of everything was $4.15

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-Typos courtesy of my mobile phone.

I remember when I did the first belt change on my 85300SD. I stopped and looked it over at great length and looked in the owners chassis manual to see how many bolts were involved. After that no problem and did not see any need to drop the alternator. That said I did miss the 17mm locking bolt on the rear and bent up the adjuster. After I straightened it out I reinstalled and after 3ooo miles have had no problems. After using the adjuster correctly it is a very good design. Just my 2 cents

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

great idea on the eye hook.
i will be doing this.
im going to try and find one that is the same thread as the original busted arm so i can use the original long ferrule.

woot

Hey folks, I have a broken alternator adjuster bolt (or pass through bolt?) on my '84 300 turbo diesel. This is not the tension bolt that okyoureabeast was referring to, but the one next to it and closer to the engine. It goes in the hole next to the tension bolt (yellow arrow in photo) and passes through to the opposite side of the alternator. Both sides are 17mm. I was loosening it before releasing the tension to replace the alternator belts and it snapped in the middle (other photo).

Does anyone know what this bolt is called or if its possible to order a new one? I haven't been able to find a parts number. Also, do you know what part of the alternator it passes through? I'm wondering if a bolt with the same specs will work, or if it needs to have exactly the same length/amount of thread as the original bolt. Is it just passing through housing or something else? It was covered with oil when I took it out... thanks!

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Just a regular metric bolt, doing nothing special. Take the old one into Ace Hardware and try to match. Ideal if they have a grade 8 w/ the yellow chromate coating. Re-use the thin washers and nut. M-B doesn't make nuts, bolts, O-rings, bearings, and such so no need to limit yourself to dealer parts. I once needed a bearing inside a Mopar transmission and saw $70 prices and weeks of delivery as an "auto part", so searched and found it was same PN as a common trailer wheel bearing with multiple choices so sprung $6 for the better Made In Japan choice, on the shelf locally.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Thanks BillGrissom! I took it to Ace and they said it was m10 x 1.5 ~5" grade 8 would be best. They didn't have that size and I ended up at Autozone, where I actually decided that 3/8-16 (grade 8) 5" was the closest fit. I eventually got someone to look it up for me and that's also what they had in their system for the '84 300td alternator bolts. I eventually got it back in and now I see that you're right - nothing special, it just holds the alternator in place.

I would not use the 3/8 bolt if it were me. It is slightly smaller in diameter, and will not work a well as an m10. It may suffer the same fate as the other bolt, but sooner. Vibration is a common problem with these engines, so tight fitting fasteners is very important. There are other sources for metric bolts. You probably have a fastener store near you (most large cities have them). The SAE bolt may work in the short term until you are able to source the proper metric bolt. I probably have a dozen of them, and I would give you one. However, finding one locally would probably be less expensive and faster than the postage cost and transit time through the mail.

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All Diesel Fleet
1985 R107 300SLD TURBODIESEL
2005 E320 CDI (daily)

LOTS of parts for sale!


EGR block kit
http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html

1985 CA emissions 617 owners- You Need This!
Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst.

Sanden Instalation Guide (post 11):
http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html