The '81 has the larger water pump pulley and uses the longer belts.

What belt length do you have? If it's 1000 mm, it's not the correct size. 1040 mm seems to stick in my head.

Check my thread titled '83 617 correct belt size.
In a nut shell, I used 1100mm belts, got 'em started, with a bump switch, (pic) walked 'em on.

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83 SD

84 CD

The 1037 belts fit my '82 300D with no problem:

http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1CQ0J3JZ42AB136NSH&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1982&product=W1002-12269&application=000032224

Its a 1035 belt and a continental made one clearly specifies OEM match.

Well, short story long, we removed the alternator slipped the belt on and tighted the alt back up using the gages for tension, All is well, but what a PIA. I lost more money trying to make it work than i would had to pay a Firestone shop...

Then we go get the filter kit to change tranny oil..wrong one and tried twice..IDIOTS work at O'Reillys Seriously!!!!

Live and learn..I LOVE MY MB!!!

Thanks to ALL of you guys....YA'll ROCK!!!!!!

Dakota

But now you'll know the next time you change the belt how to do it, and it will only take a few minutes instead of all day. Thats how it goes sometimes, I've been there several times.

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If you did manage to get the belts on; what if they were too tight and there was no way to loosen them? If you ran it like that it would damage the bearings in something; alternator or water pump.
Better to take the time and try and get some slightley larger belts.

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84 300D, 82 Volvo 244Gl Diesel

Oddly, my CD uses 1035's.

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83 SD

84 CD

Thanks for all your help people, now my kingdom for the right size tranny filter and gasket....i dont want to order, I cant wait fir the part..maybe auto hell (zone)

Good luck with that, the gasket is oddly shaped so a measurement won't help, and if undamaged, can be reused.

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83 SD

84 CD

I recall using some sort of shadetree combination of loose alternator bolts and brute force with a long screwdriver and some other implement of automotive destruction to change my belts... it wasn't fun.

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99 E300 Turbodiesel 100k

I understand that this may be a little late, but, in my experience (which is limited) I had the same problem trying to get the alt. belt on my 240. My solution was to get as much of the belt on the pulley and bumped the starter. All that who ha about heating up the belt was erroneous. Because that belt that appeared to be too small is gonna stretch after a few days of use and then you'll encounter the mystery of the ever self loosening alternator bracket.