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?

__________________
'87 300D, w124, 171k
'82 300CD, w123, 200k or so. (sold)
'82 300TD, w123, 168k (sold)
'81 300D, 118k, w123 (sold)

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

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

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...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

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

__________________
'87 300D, w124, 171k
'82 300CD, w123, 200k or so. (sold)
'82 300TD, w123, 168k (sold)
'81 300D, 118k, w123 (sold)

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.

Attached Thumbnails

     

__________________
'87 300D, w124, 171k
'82 300CD, w123, 200k or so. (sold)
'82 300TD, w123, 168k (sold)
'81 300D, 118k, w123 (sold)

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

__________________

85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

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!

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

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.

__________________
http://i193.photobucket.com/albums/z...-RESIZED-1.jpg
1991 300E - 212K and rising fast...