Bump ...

 

When you say you ordered new "pulleys" are you referring to the idler pulley (what MB sometimes calls the sheave pulley)?

The most common reason the belt falls off on these engines is idler pulley failure.

Another cause is cord breakage within the belt (think of a tire cord) that allows the belt to flex laterally under tension, then it flies off. You can't often see this just looking at the belt.

The tensioner you are replacing, which is another potential cause.

Otherwise it would be related to any other rotating accessory binding up (usually this doesn't cause the belt to fly off, but rather burn) or failing in one way or another (bad bearing allowing the pulley on the accessory to orbit rather than stay fixed in one plane).

So while you have the old parts out of there, be sure to inspect all of the other rotating accessories to be sure everything is solid and turns freely with no excess free play. May as well eyeball everything to be sure the pulleys all line up properly, too. If everything is otherwise okay, then swap the idler pulley and tensioner, then fit the new belt and you should be good to go.

Good luck.

 

Thanks, man. Replaced the tensioner no problem. About to do 3 pulleys but need to figure out how to get the old ones off. As for the rest, alas, upon inspection of all the rotating "accessories" - I just noticed what I assume is a major problem -- and what caused the belt to slip in the first place. The very bottom pulley is loose as a goose. I won't be able to see what's going on until I pull the radiators :eek

More to follow.

 

The bottom pulley...that would be the harmonic balancer. It does work pretty hard on the big V12.

I'm glad it didn't grenade and do lots is collateral damage.

There was a recall back in the day, I posted about it in the general forum. I can't recall If your PN is included, but if so, call the dealer.

Good luck.

 

Right ... the harmonic balancer. Well, I thought I got lucky when I was able to remove it (by simply backing out the large bolt in the middle with a 24mm (? may have been 25; can't remember) socket, inspect it (it looked OK), and re-install it. Torqued the bolt enough to take the play out of the pulley. Everything looked good, so I started the engine ....

and the belt slipped again.

Wish I had tested in before re-installing the bloody fan & shroud assembly:eek

Back to the drawing board.

 

Boo - I might have some info on your problem here. See the details on the WIS drawing below.

1. You should not ever 're-tighten' this pulley bolt. For certain applications, MB advise that the bolts should be replaced, as the threads on the new bolts are specially treated for a one-time operation.

2. You are possibly not using the right torque. It is 200Nm (stage 1) plus 90 deg. (stage 2). You will need a counter-holder here, in the right position.

3. You should also examine the pulley for 'lateral trueness'.

 

A HA !!! I was wondering why a few threads specifically mentioned using a new bolt each time ... even if you only backed it out once as part of a trial and error troubleshoot. Many thanks! Wondering if a new bolt would do the trick, then? I may try it, as my dealer tells me that there are no HB's available in the US and that getting one from Germany will take 5-8 business days. The bolts and seals they have. Wonder what the fastest way is to procure that special wrench that holds the pulley in place while you tighten the crank bolt? Anyone know if that's a dealer item? I know they're not cheap, and it chaps my @ss to pay that much for a wrench that I'm hopefully only ever going to use once, but such is life with a $170k car, right?

Many, many thanks.
Will report out.
Much peace.

 

"You are possibly not using the right torque. It is 200Nm (stage 1) plus 90 deg. (stage 2). You will need a counter-holder here, in the right position."


So once I have the wrench in place, I tighten to 200nm, and then go a quarter turn more? Sorry if that's a dumb question, but I'm in terra nova here ...


Thanks !!

 

^^ That's correct.

What PN is the HB presently installed on your engine?

 

I can't quite read it. Pictures attached ...

 

ECS says it ships in two days: 1370350200 - VIBRATION AB - ES#1678732

Dang expensive part. There are some used ones on ebay for a decent price, if it is in good condition with a warranty that may be an option.

If the rubber has deteriorated at all with yours then it's likely to be that the pulley is slipping. Even if the bolt is loose the key keeps the core from moving relative to the crank.

You can use either P/N 1370350200 or 1370350300.

Good luck.

 

FWIW, the dealer tells me that the part I need is M2750300003. When I googled the PNs referenced by Check Codes (and followed link to ECS), it tells me that those will fit cars up to 2002; mine is a 2003. Technically, I believe it's a 2003.5; at least that's what the previous owner said. Kinda weird if it's true, as the VIN indicates it rolled off the line in late 2002 ....

I know we all like to bash dealers for their prices, but I have to say that whatever premium I'm paying (vs. buying on line) is more than offset by the excellent help and guidance I've received from the chaps at Euromotorcars Germantown. I only wish I could get it sooner ....

 

My bad, I was looking at the prior year. 2750300003 is the correct P/N. That said, the original P/N was 2750350100 (that is yours as pictured) so the part has been superseded, which also suggests there were problems.

This one on ebay is the newer part, it's $100 and it's in Santa Rosa with $10 shipping. It is used but it looks to be in excellent condition. All other things being equal I'd certainly give this a shot since it is the newer part.

Good luck.

 

My idler pulley disintegrated causing a shredded belt last month. Check that out too, make its in good shape.

 

Yeah ... this all started with a simple idler pulley & tensioner replacement

:eek

 

Photo of 2001 CL600 engine.

Booesq;

Sorry to hear about your pulley problem. Here are photos of my donor car 2001 CL600 engine after we pulled it out. It shows the aforementioned pulleys quite well. As they say, a picture is worth a thousand words...

Best of luck.

 

^^^Great picture. I've never seen a V-12 pulled and fully-assembled, and I'm most amazed at the size of that gargantuan alternator. For a cool gs (rebuilt, no less) it should be impressively large, I suppose.

Booesq, how's it coming? All these years wrenching on cars, I've never seen a sheared woodruff key. Sadly it sounds like it's as ugly as I'd imagine.

 

VICTORY !!



Sorry for dropping out of sight. Life got crazy busy, and I wasn't able to get everything back together until this weekend. I'm very pleased to say that this ungodly P.I.T.A. effort all worked out. I managed to remove the old key, insert a new one, install the new balancer (and bolt!!), etc .. Once everything was back together and the fluids topped off, I said a prayer, turned the key, and .... Voila! We're happy (... or so it seems). Just a few final notes / thoughts:

- I did manage to remove the old woodruff key by drilling it out VERY carefully. I used a cordless 18v impact drill, half a bottle of cutting fluid, and a magnetized probe to remove the key shaving by shaving. Yeah, it was that crazy. Oh, and at least a dozen hardened drill bits.

- As the old front seal had been removed in anticipation of replacing the same (as recommended by everyone), I packed a rag into the open space around the cam snout to prevent any material (e.g., key shavings and the tips of broken drill bits) from falling into the engine.

- In order to get the best view, grip, and leverage, I had to remove all of the radiators as well as the radiator cross-member and the electric fan & shroud.

- Installation of the HB without the tool from MB that was specifically made for the task would have been impossible. On some other MBZs, the crank bolt that secures the HB is not only hexagonal on the outside (so you can turn it with a socket) but also has a hexagonal aperture in the middle (so you can turn it with a large allen-type tool). Not so with the M275.

- And speaking of crank bolts, I'm nearly positive that the problem was caused by a prior owner's removal and re-installation of the old HB, albeit without replacing the crank bolt. I noticed that the old one had traces of blue lock-tite on it. That just won't do, friends. It's an expansion bolt which stretches when torqued to spec (200 nm + a quarter turn) and is a one trick pony. Please don't ever do what that knucklehead did. I know it hurts to pay, what, $14 dollars for a single bolt, but the if you think that's expensive, consider the cost of a new engine:eek

That's all for now; gotta get back to work. I can't possibly express my gratitude to all of you for your input. Never could have done it without you.

Much peace,

c

 

Water-cooled alternator.

CheckCodes;

You are indeed correct in saying the water-cooled alternator is large and expensive to replace. My 2001 AMG CL600 is on its third one (81k miles). If you study the photo, you'll notice the crankshaft pulley is three times the size of the alternator pulley. The next time you redline the motor getting on the autobahn, remember your alternator will be spinning at 18,000-rpm...

Regards,

 

All good news in the end.

Hopefully you get lots of trouble-free driving for some time that you have paid your penance to the MB gods.

 

Out of the frying pan, anyway. Not quite into the fire, but now I'm having a heck of a time getting my radiator sealed properly. Lower "T" fitting @ bottom of radiator keeps popping off, and each time it does, I lose a king's ransom in coolant ... Think there's a thread on that somewhere.

But yeah, the motor seems to be quite happy. After dealing with the woodruff key, I'll take a cooling system glitch any day of the week!