Alternator Pulley NUT Un-threaded itself
 

Alternator light has been on for the past year. Had a bad diode that was not converting all of the AC over to DC. Finally got around to putting in a refurb a few weeks ago.

Last weekend I was poking around under the hood and noticed that the long "nut" that threads onto the end of the alternator adjusting bolt was missing. I remember tightening that baby down with a 10mm and found it quite odd that it had un-threaded itself. I put a regular nut on there until I could get a replacement (still looking).

Today I notice this really odd clatter noise on the drive home. I pull over check the belts and such, all seems well. When I get home I take a closer look with a flashlight while the engine is running. The alternator pulley seems to have a very slight wobble. Turn off the engine and check the alternator and the bolt that holds the pulley on is missing?!

Kind of odd that both nuts have un-threaded don't you think? As my leaking oil and transmission pans will tell you I am one to over tighten and opposed to under :). Should I have used loctite on the pulley bolt? Anyone else had this happen?

No loctite to my knowledge, just an impact wrench. Odd that both did it. Weird vibration I'm guessing.

Assuming that the bolt was actually a nut, did it originally have a corrugated washer under it?

... I'm sure you meant you remember tightening it down with a 13mm...

Yes, nut. No, I do not remember there being a washer.

I was able to pull the alternator off of the car this evening. A small piece of metal fell out when I pulled the pulley off. The 1st picture is the area where I think the metal broke from and the 2nd pic is off that area and the small piece of metal.

Can anyone confirm that piece of metal should go where I think it does? If so, if this broke would this cause the the bolt to un-thread? I would imagine this would be the cause of my why my bolt un-threaded in the first place.

Second question is in the 3rd pic below does that look like the correct assembly for the pulley? Right is bottom working left?

Thanks is advance.

http://www.peachparts.com/shopforum/...1&d=1287028125

http://www.peachparts.com/shopforum/...1&d=1287028125

http://www.peachparts.com/shopforum/...1&d=1287028125

i think that piece of metal is called a woodruf key or something...it's supposed to stop whatever is attached to the shaft from rotating independent of the shaft...
the notches on the pulley and the fan go over that key

that alt is shot.
as beat up as the keyway and key are, you will never get another pulley lined up well. bite the bullet, and get yourself another alternator.
likely, the pulley is just as bad. be sure what alternator you get has one installed.
best bet would be to pull one from a yard.
save your regulator if it's in good shape!

The loose alternator pulley problem recently occurred on my 1993 w124 300D . I guess that the PO did not torque the nut correctly on a replacement alternator. It threw the serpentine belt . I haven't removed the alternator yet but presume that the pulley setup is the same as shown above - nut>lock washer>pulley>thrust washer .

Someone mentioned to me that the "compact " alternators on the w124 models do not have a woodruff key . Y/ N?

I guess that I'll use this tool - http://www.peachparts.com/shopforum/diesel-discussion/310370-1995-w124-e300d-alternator-pulley-tool.html
or similar and some red loctite to make sure the nut stays in place.

BTW - What is the purpose of the plastic "bowl" and hose on the back of the alternator ? How do I deal with that in the R/R process . My friend's w201 190D does not have that .

Edit- I took the "bowl" off . I guess the newer alternators don't have it. Unfortunately, the upper alternator bolt is frozen mounting bolt (a very hard long handle rachet won't loosen it. I am concerned that I will strip the threads and will soak whatever cracks I can with Pblaster and try again in few days) . Also, I saw that one of the fan blades was damaged when the serpentine belt was thrown off (: darnit .

Thanks

Ok, I got the alternator off . Those two mounting bolts will go back with some anti-seize compound on the the threads. I removed the nut from the alternator and did not find any kind of lockwasher (eg. serrated washer etc) behind it ( nut>pulley> alt fan> thrust washer), no keyway . Is there supposed to be a lock washer between the nut and sepentine belt pulley on this one (w124 300D)? . - Thanks

No woodruff key on my stock alternator...or the 120AMP alternator I pulled from an W140.