Another weird noise in my 300SDL
 

I dunno, hate to seem paranoid but this is funny and not funny ha-ha. Almost sounds like a playing card in bicycle spokes.

https://youtu.be/Wte_EDFQgWE

I found this one from about a year ago to compare:

http://youtu.be/c21_xj4mesc

*ETA*

I'm wracking my brain to try to figure what, if anything, I might have lapsed on. I checked the oil when I first heard this sound, it was maybe 1/8 inch about the min, I'm about to change it. More important, I may have gotten slack a time or two about putting in enough lubricity additive. I'm running on HPR, the 2nd gen biodiesel that CA brings in, I gather one should use the lubricity additive. I've been using Howes Diesel Treat, one ounce to 5 gallons, usually more than that.

Maybe I'm tripping here, dunno. I'll put some extra in before I go anywhere, though I suspect if any damage has been done that horse has left the barn. I've seen no driveability issues in the last few days, power is good. Another odd bit, from the two vids it seems like the idle speed is higher now. My tach says about 700.

Tensioner shock or tensioner pulley worn out. They make that high frequency "chatter" when they crap themselves.

You mean this guy?

https://i.postimg.cc/9M7g451P/tensioner-lever.jpg

And this is the shock, I think:

https://i.postimg.cc/BQz01sBk/tensio...oner-shock.jpg

The dealer has the shock on the shelf - $93. Pelican aftermarket - $31. I was hoping to make a trip this weekend, might not work.

By the way, I’m liking your diagnosis doctor. Carefully taking note not to chop off my fingers with the spinning fan blade, I carefully touched my mechanics stethoscope to the lever body that holds the shocks and it sure sounds like that’s where the racket is coming from. No other parts that I touched give nearly as good a report. Looks like there’s two shock observers there.

Seems to me that a bad bearing in the pulley would be the source of the noise but you have more experience in this issue than I do, that much is clear.

Looks like I’ll need to take the radiator out to do this job. Once I get the parts.

Might as well replace the spring and pulley also - my spring broke about 5k miles after I replaced just the lever. Parts from Pelican, that was about 10-15k miles ago - so far so good.

Yeah, I’m thinking to replace it all. Hard to get in there, may as well do it right. I found a place here locally, not your normal chain auto parts store - Kohlweiss. They can get me the parts this afternoon, after market, but I think I’ll go that route here.

What I can’t figure, it looks like there are two shocks going on but he says only one is required. I’ll look closely when I get back.

You can do the job without removing the radiator. One of the shocks is the shock you linked, the other is a spring in a rubber tube. Release tension and rock that tensioner pivot back and forth. If it seems loose and sloppy, or if it feels tight and gritty, its needing replacement. If it's smooth, leave it alone.

Replace the shock and the spring as a pair. If the tensioner pivot needs replaced, you can do it without removing anything from the engine. It gets TIGHT against the fan, but you can do it. If the pulley on the tensioner needs replaced, now is the time.

Usually the tensioner parts are ok, it's just that shock that wears out and causes a heck of a racket. As mentioned above, the spring usually fails soon afterwards from stress, so it's a good idea to replace it preemptively.

You’ll need a 12mm hex bit for the tensioner arm bolt.

Sixto
98 E320s sedan and wagon
02 C320 wagon

Good call, I think my biggest is a 10mm. I'm guessing it should be the L shaped variety rather than a socket. Might have 12 in a socket.

I wanted to change coolant today, taking the radiator out wouldn't be a huge problem. But I'll look it over.

The torque spec for the tensioner arm bolt is 50- or even 70 lbft so you need a socket rather than a key. Go easy on that bolt. MB added internal ribs in each of a handful of front cover redesigns.

Sixto
98 E320s sedan and wagon
02 C320 wagon

This must be the spring, eh?:

https://i.postimg.cc/9M7g451P/tensioner-lever.jpg

(I'm not Canadian, 'say what?' seemed a bit much)

The shock is an easy replacement. My existing shock had full resistance one way, but no practical resistance the other. The bushings that the bolts go through we’re stuck in tight, but spun almost as easily as if there were bearings. The new one had fully tight bushings.

It made a marked, substantial difference in noise and smoothness.

That is the "Belt Tensioner Lever for Tensioner Pulley". The belt tensioner spring connects to driver side of that lever and the belt tensioner shock connects to the other side.

This was a challenge. I undid the top bolt on the shock absorber but on the bottom, I got it unscrewed, tried to slide it forward, no can do. Will not come out, the pulley stops it. Nor can I pull the piece upward, the bolt is still inside it somewhat.

One option is to take the water pump pulley off but to do that I first need to take the fan clutch off. If it was my BMW E30 would have been off 15 minutes ago. It takes an 8mm allen socket just fine but which way to turn it is the question. Neither way wants to break free. My bimmer has reverse threads on the fan clutch, that way you don't even need to tighten it seriously as the clockwise direction of the motor will act to keep it snug. I sorta hate to bang it with hammer to break it free if I'm going the wrong way.

I was in trouble with the bolt on the bottom of the shock, couldn't screw it back in so I cut it off, easy enough to get another. While putting it together I'll practice with a doable method to swap the shock w/o pulling the radiator and fan. I read that the shock can have short lifetime.

I get the rest of the parts in the morning, was just prepping. I'm glad I got a new Belt Tensioner Lever. The old one has some slop in the movement.

Put an OAP pulley on the alternator and never have to worry about the tensioner again.

I’ll look into that, but I need to get this thing running and that will take a while.

The question that is stumping the panel at the moment is how to get the GDed fan clutch off. The nut holding it is in the end of the water pump shaft and I can’t figure out how to grip that.

I'm starting to thing that when the water pump gives up the ghost, I'll somehow get it off and put the impeller arm in a vice and take the fan clutch off.

Sorry, I’m just not seeing how the tensioner shock is a challenge. I just did the tensioner shock on my 350sd this weekend. It wasn’t more than a 15 minute job, including finding tools and some anti seize.

I got that bottom bolt out easy - Id find it hard to believe that the stack up length of a 603.96 in an sdl is shorter than the stack up of a 603.97 in an SD.

The key I found was to remove the spring and loosen the bolt a bit (ratcheting wrench is helpful, use the lug wrench to lever the tensioner up against the water pump, then just pull the bolt by hand. Sliding the belt off ever so slightly and getting the tensioner up like that allows the bolt to be removed. At least on mine that I did this weekend...

Fan clutch Ian a different beast. Believe you need a tool to lock certain items in place, then remove the fan blades and so on.

W126 FSM is available free from MB. I didn’t realize that cars this new were available free until recently. Have you looked in there for the clutch job?

Why does the fan clutch need to come off? Just keep maneuvering things around so they clear the fan blades. The bolt for the tensioner lever will clear the fan/clutch assembly by fractions of a millimeter (yes, it's REALLY tight) but it will come out without having to pull the fan/clutch assembly. See my thread from this past winter for what a nightmare that job can turn into (especially when some asstard installs it with a rattle gun!)

I'm not sure why some of this turned into such a hassle. Hard to describe, but that lower bolt on the shock gave me grief. I now see that if I'd taken the spring off first would have been easier.

I was wanting to replace the lever arm and the idler pulley because 330,000K. The old lever arm did have some play in the bearing it turns out. Not sure that would cause grief but the new part wasn't expensive. I may regret going aftermarket on this, somehow the idler and lever don't seem that high tech, the shock I will get MB next time.

The 6mm allen bolt on the idler pulley was in bad shape. At first a 5.5 was all I could get in but sloppy. I did the math, 7/32 a hair bigger than 5.5 but also sloppy. Looking at the orifice with a mirror it almost looked round. My shade tree ass told me that bolt would be normal thread but no way do I want to crank hard on a sloppy allen fit. I eventually put the 6mm Allen socket in and tapped it with my little jewelers hammer, that did the trick, was just bunged up, it broke free but wow, it was a hard break.

Uhh, say what? MB is giving away free factory service manuals for 30 year old cars? Why wasn't I told! No but, that is something to look into. A couple of times here I regretted not already laying my hands on whatever I could get. Youtube vids will only go so far. I sorely miss the Bentley and Haynes manuals I used to good effect for years on my E30. A Bentley for the 300SDL would be sweet but I'm guessing there were 10 times as many E30s made/imported.

The fan clutch is a PITA. Will need to research that. Water pumps don't last forever.

What got me into trouble with the lower shock bolt was loosening it while it was behind the water pump pulley. Once it came out I was having a devil of a time getting it threaded back in,. Some damage somewhere, could not finger tighten it, getting a wrench on it, even my little 4 inch box/open combo, was like pulling teeth.

My 12mm Allen socket would no way work with the idler pulley in the way. I still had the belt on at that point. Maybe with it out of the way it would have worked.

The spring on this gave me some trouble. Have got to find the magic sauce for levering it to move it where you want. I am really appreciating the General Motors tension spring set up for the serpentine belt on my old G20 van. Piece of cake. You twist the bolt on the end and it cranks the spring backwards - slide on belt, release wrench and there you are.

You are right with that!

The little hole in the plastic piece to remove spring tension is slick and convenient, but then we end up with a stupid tensioner design that is levered against the water pump.

That little bolt that holds the lower shock connection to the tensioner arm need not be tight. But getting and keeping it in the right spot is a pain. Only five minutes worth of hassle, but still a pain.

As I recall, with the spring and idler pulley out of the way the fan and water pump pulley don’t have to come off. The tensioner arm will pivot enough to make the damper lower bolt accessible. The OE idler pulley bolt takes a 5- or 6mm hex bit. I only have those two sizes and I’ve never had a problem.

If it hasn’t been said, the fan clutch is held by a regular right hand thread bolt. Hopefully the 603.970 water pump has the tall ridge like the .971 water pump that lets you slip a holding pin into the backside of the water pump pulley. The .96 water pump has less of a ridge that won’t hold a pin. Or use a tool that holds the rim of the pulley. There’s a MB special tool that easy to fabricate. It’s a pity HF stopped selling this but it should be available elsewhere -

https://media.napaonline.com/is/imag...ompany/1573720

Spend some time with an M103 belt tensioner before you call the 603 tensioner the worst.

Sixto
98 E320s sedan and wagon
02 C320 wagon

I did this recently, on my W140, and I did not have to remove the fan clutch to replace the shock, lever and spring.

When I did replaced the fan clutch I used a strap wrench on the pulley with a block of wood between it and the pully - it worked really well, belt was off of course. I vaguely remember that on my .971 that a holding pin in the water pump pulley was not an option.

Back together, noise gone. I see now the error of my ways. The tensioning process not that tough, swapping a shock absorber also not that tough. I need to get the FSM. How does one get this free manual?

I think I owe Diseasel300 dinner someday.

W126 FSM link below:

https://www.startekinfo.com/StarTek/outside/12253/?requestedDocId=12253

Little tip for those trying to deal with the stupid tensioner design. That hole in the upper plastic pivot piece is perfectly sized for the handle of the tire lug nut wrench. I cussed MB 7 ways from Sunday until I realized it was *ME* that was the idiot using the tensioner.

Insert wrench handle. Remove nut. Lever on wrench to take tension off bolt, push bolt back and pull the head from the rear to clear the plastic pivot. Release tension on wrench handle. Remove spring.

Then you can do whatever you need. Re-routing the belt is still a major ***** but the lower pivot can then spin freely without obstruction.

The FSM makes changing the lower tensioner pivot into a major ordeal. Not necessary.

Removing the fan clutch, however, IS a major ordeal, especially if someone jackhammered it on like they did mine!

Question re pulley
 

Does anyone have a part number or link to an OAP alternator pulley for a 124 OM603? I recently changed the shock and the tensioner and I am still getting some noise from that area.

This is from my 603 tensioner shock thread:

if I had looked at it more closely like I did when it was apart, I might’ve figured it out. It’s a pretty good design all in all. I saw that plastic part and thought to myself, it has to be that way for a reason. On the fan clutch, I don’t like a nut fastened that tight to the end of the bleeding impeller which is only too happy to leak if abused.

A long 3/8" ratchet extension also fits. :)

Mine was a tad too big, turned out my 1/4 ratchet handle fit perfect. A bi short but sufficient leverage nonetheless.