Missing alternator tensioning bolt?
 

Hi, this is my first post and I just bought a 1980 240D it does have a few problems but it is going to be a project car (I want to produce my own biodiesel for it to run on).

One of the problems that it has is a belt squealing at start up which figured is a loose belt that is easily fixed. I have seen the problem before and thought it was easy but I was wrong. It looks like I may be missing a tensioning bolt but I can't tell.

I looked at a ForcedInduction post where he attached a couple of images of the possible alternator belt tension systems. I have the attached images from his post here.

On my car none of these images match up. The closest think I may have is from the third setup but the number 4 bolt is a lot larger. I do have a couple of links with some blue circles to where I think I may be missing a tensioning bolt and the larger (17mm) bolt.

http://imgur.com/p7az6.jpg
http://imgur.com/C0s2S.jpg

Thank you for reading and since this is my first diesel I hope to learn a lot more and contribute to future diesel owners.

In the P7az6 Pic. Someone has replaced the original Bolt with the one in the Circle.
To tighten your Alternator Belts you need to loosen the Nut that is on the other end of that Circled Bolt and stick something down there so that you can lever the Alternator to tighten the Belts. Maintain leverage/tension on the Alternator and tighten that Bolt/Nut. (Just like it was done on all of the older Amierican Cars I have owned in the past.)

A replacement Bolt will cost around $40. As you seen in the attached pic it had a long Skinny threaded Shaft coming out of the Hear of the Bolt. And, there was a special Captive Nut that went into that Circled Ushaped Slot in the C0s2S pic.

2 problems with that set up were that people would forget to loosen the nut on the Big Bolt and start turning the Special Tensioner Nut and shear off that long Threaded Shaft. Or, the Special Nut would rust on to that long skinny Threaded Shaft and people would turn it and shear it off.
Due to the replacment cost of the Bolt a previous owner decided to use a regular Bolt.

In the Below Pic the Arrow on the Left points to the Adjusting Bolt and the Arrow on the Right points to the special Nut (yours is missing) that would thread over that part of the Bolt.

Wow I have never seen anything like that before, I just kept looking at it thinking, "how in the world...". I thought something was missing and I am very glad I was right. There is a bolt at the bottom of the alternator that I didn't take a picture of that the alternator hinges on (I think). I loosened that up first and then the bolt and nut at the top and it came loose but I can't seem to get it back to it's original tension (even though it was loose to begin with, it is worse now).

Now this bolt I am assuming the thicker end would go through the alternator and the thinner would go through the U-shaped slot with a nut to give it tension? If that is right where can I purchase this?

EDIT: Never mind the first question then, for some reason I am getting the responses late on my computer. Thank you for all the help Diesel9112

EDIT 2: Found it and purchasing it

Where will you be getting the Special Nut (the bolt does not come with it). I did not see the Nut for sale at my favorite Prts Place.

It is hard to tell from the Pic I posted but the Nut is somewhat like a Rod Coupling Nut (a nut that is about 4 or more times longer than a regular nut) and it has a Groove machined around it about 1/4 inch or so from one end of the nut. The Nut slides into that U shaped slot and is held captive there.

I was going to use 2 nuts and a washer to get the tension. I haven't even looked for the special nut that goes on the thin end of the bolt. Since I have only owned this car for about a week I haven't dealt with this problem before so I hope that works.

Now the bolt itself I purchased at autopartswarehouse.com, I just did a search for the bolt and it was one of the first places that I saw that had the bolt. I will be getting the bolt in on Monday and then I will take it to a hardware store to get the right nuts and washer sizes on Tuesday. I should know by Tuesday night if my idea will fail horribly or sort of work.

Your idea may work fine. Maybe the Hardware Story might have some Nylock type nuts. Having at least one selflocking Nut could be helpful.

Yours is the second / right hand picture from Forced Induction (same as mine and probably most in the US). You can see the long nut in that picture. But like D9112 said you could just do it the way most old cars did, tightening the bolt while holding it to the right tension with a bar. But it sounds like you might have to tighten the nut on the other side (back) of the alternator, which might make it a 2 man job. But you could get the adjusting bolt and long nut dirt cheap from a wrecking yard, makes it a lot easier to adjust it.
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Ef engine

Thanks Paddo,

Since I ordered the bolt I have since installed it and purchased the self locking nuts and washer to replace the special nut. Now it works very well, I was having a squealing noise made from the belt at start up. The belt is tight and the squeal is gone. If you want I can take a picture of what I have but it is pretty self-explanatory.

If you could be bothered to take a pic I'm vaguely curious how you set it up, but no biggy.
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CHEAP EASY VAPE VAPORIZER