My half pulley slapped my radiator. 1982 240D - PeachParts Mercedes-Benz Forum

CarolinaMBZ · #1 07-28-2004, 03:17 PM

Looking for insight from those who may have had this happen. Several weeks ago, I reinstalled my original alternator pulley halves as part of an alternator replacement and belt replacement on my 1982 240D. In closer observation of my recent radiator leak last night, which was coincidentally just in front of my alternator, I loosened the fan shroud and heard a loud clank. Looking down I saw one-half of my pulley half on the driveway.

I am interested in other's experience in why this may have occurred. I don't believe that my new belt was installed too tightly. I also believe that the washers and nut were all propoperly sequenced. Do these pulley halves just wear out and become overstressed? Or is there something I failed to do properly?

As always, all help is appreciated.

BTW, separate but related question, my new Behr radiator has fittings for AT cooler lines, which I don't have because I have the factory hot rod set-up (Manual transmission). Did I get the right one (my existing one has no such fittings that I can see (still in car, but that is the reason I was loosening the shroud))?

leathermang · #2 07-28-2004, 06:10 PM

I think we need some pictures of this in order to give you good info... any chance of that ?
There will be physical clues ... just like a crime scene... it is just a question as to whether you can find them of get a good picture of them.... We will try if you can...

KCM · #3 07-28-2004, 06:44 PM

I had a different experience with one of those two piece alternator pulleys. I had just bought the car and replaced the belts with new. I drove the car for a while, and the alternator belt became slack. I tightened it and drove the car about 150 miles before the alternator belt started to self-destruct and wear the V off, and at 300 miles it was toast. Thinking it was just a crappy auto parts store belt, I bought another brand, a Gates. Put it on and in another 150 miles the belt started to loosen from premature wear. All pulleys were in line, and the only pulley that looked odd was the alternator pulley. Took it off and it showed some wear and waviness in the V face. Figuring that this must be the cause, I ordered a new pulley from an aftermarket parts place. The new one was a one piece solid steel pulley, a world apart in quality from the cheap two piece original. Put it on and my problems went away.

By the time I was done, I had bought three belts ($15 each), alternator brushes (thinking the alternator was not charging instead of the belt being loose, $40), battery (from the alternator not charging with the loose belt and almost leaving me stranded, $45), and a pulley ($35) for a grand total of $165 just because of a poor quality pulley (in my opinion).

CarolinaMBZ · #4 07-29-2004, 10:39 AM

Leathermang: All I have is the one-half circle of the pulley half. The other pulley half (front one) is still on the alternator as is the belt. I will try to post a picture if you think it will help. The idea is for me to avoid having my new radiator stabbed by a new pulley half-half that breaks in the future if I am doing something wrong and at the same time perhaps prevent destruction of some other forum user's too. I appreciate the help.

KCM: Where did you get that one piece and was the notch the right size for the piece on the shaft that prevents slippage?

Thanks.

leathermang · #5 07-29-2004, 11:31 AM

A picture of that half that came off....
or just put it on a scanner ... once with it up and once down....
should tell us plenty...
ie, did the holes come off with it ? did it wear in two ? etc....

elusive 190E · #6 07-29-2004, 04:40 PM

Just out of curiousity are the pulleys that failed only the ones that use the older style "V" shaped belts?

Or has anyone ever had this type failure with the wider/flat serpentine style belt pulley?

Seems like failure of the older style "V" type pulleys could be attributed to a million miles between replacements or an over tensioned belt... whichever occurs first...

Only trying to brainstorm, thanks.

CarolinaMBZ · #7 07-29-2004, 08:28 PM

Hopefully one side of my pulley half is pictured here:

CarolinaMBZ · #8 07-29-2004, 09:23 PM

The other side:

CarolinaMBZ · #9 07-29-2004, 09:25 PM

Elusive: this is a V-belt pulley. Not aware of any pulley problems with the poly belt pulleys, just the tensioners failing every 60K (at least on W124s).

Benzcrusher · #10 07-29-2004, 09:37 PM

Damn....

elusive 190E · #11 07-29-2004, 09:44 PM

Hello,
That is really something about that "V" pulley...

If you could take a picture with the broken parts facing the camera... with as much detail as possible...

Digressing for a moment-

On those serpentine belt assemblies, I thought the failures were mostly caused by people trying to tighten/adjust the tension rods without first loosening the pulleyed components...

Someone broke a bolt tab off of their altenator doing that...

Thanks again, I am only brainstorming...

P.S. Nothing I love better than failure analysis...

CarolinaMBZ · #12 07-29-2004, 10:20 PM

Elusive: I don't have a camera, these were done on my scanner. I was talking to a friend of mine who was replacing his generator pulley (porsche 356) and I think these things just die from fatigue as they seem to be made from cheap metal. I think the W124 tensioners just go from the heat (especially V-8s b/c there is not a lot of air flow in the engine bay).

On the picture taking, I only have this one piece and it was scanned front and back. The shiny side is the convex side where the belt rubbed.

KCM · #13 07-29-2004, 10:46 PM

CarolinaMBZ,

That looks like the style that was on mine. Found out that Mercedes has changed the part number over the years, so maybe they modified the pulley because of problems. I still think the two piece style is a hokey way to make it. That is the first pulley I have seen that is not one piece. Your pulley must have formed a stress crack around the hole and the crack propogated, breaking it in half.

Send me an email (kcmiller.ne@netzero.net) and I will give your the phone number of the place I got the pulley from. They are not on the web. The one I got fit perfectly and will never fail.

elusive 190E · #14 07-30-2004, 05:11 AM

Hello,

Thanks for all the information...

Makes me want to look closely at the pulleys to make sure none are trying to crack whenever I get a chance to check out the older MBs...

I hope that new piece you get lasts forever...

Again thanks and good luck!

Elusive 190e

leathermang · #15 07-30-2004, 07:28 AM

Wow, that really Broke.... that was a totally different plane than what I imagined.... can you tell if any spot welds, for instance, lie on the break line ?