The larger alternator's inertia was enough to make the serp belt slip on my car when stopping the motor - it would make a little chirp.

Considering the low cost (~$60) and ease of install on the 603 I would install one even on a stock output alternator.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Great post by the OP!

A larger alternator will place additional stress on the crank and may have something to do with crank pulley failure. It would be interesting to know if there is any correlation. The cases I've seen (on the internet) have often been OM617 engines with their typical large accessory load. I've also seen it happen to a poorly maintained OM603 3.5 (in person) that was otherwise stock. I wonder if a bad idler could add enough torsional stress to loosen the pulley.

When I was researching alternators, pulleys and belt drive systems I found that the alternator is the single largest mass in the belt drive system. The polar moment of inertia of the alternator rotor places a great deal of stress on the belt. This is especially true of diesels which have large torsional vibrations at the crankshaft. Every compression stroke slows the engine and every power stroke accelerates it. Ideally these changes occur at the alternator in sync with the engine. Decoupling pulleys allow the alternator to freewheel when the crank decelerates.

Serpentine belt systems gain their power transmission efficiency advantage from their thin cross section. This reduces hysteresis loss when the belt bends around a pulley. Compared to a 3 or 4 v belt system the fuel savings add up. Unfortunately the willingness of a serpentine belt to bend easily also causes flutter. When designing a serpentine belt system the position, tension and damping of the idler becomes critical. Decoupling pulleys reduce belt flutter in serpentine systems simplifying belt tuning. The decoupling of the alternator's mass also saves fuel. Manufacturers have adopted them almost universally.

This link has some good information on (mostly Denso) alternator output and at one time they specified the polar moment for their alternator rotors though I can't find it now.

Alternators | Electrical | Products | McLaren Applied Technologies

When I decided to update the alternator on my 220D I contemplated adding a larger alternator with a serpentine drive system and a decoupling pulley. I ultimately decided against it when I measured my stock 35 amp alternator and measured my full load power consumption. I went with a NOS 40 amp mini Denso from a Kubota diesel tractor and a conventional V belt drive system. If you need a high power alternator like Greazzer does for his project then a decoupling pulley might be the way to go.

Either way make sure your crank bolt is tight!

__________________
1969 220D 5 Speed (OM616)
1983 240D 4 Speed
1985 300D Auto 376K
1985 300D Auto 275K

I put a solid pulley on my 1998 E300D on a while back when my oap broke. I ignored the squeaking and bearing chirping for about 3 months and finally it just broke off. Lucky i was in traffic an going slow and just pulled over. The pulley was still sitting there with the belt on it.

The alt rebuild shop didn't have the oap in stock and suggested use a solid one and neither of us knew any better and liked the idea. Now I know. Thanks RTH.

Ill try to get a video of that car with the standard pulley. It's my friends car now. The only difference i noticed was the battery light comes on every time you start and stop the car. Why is that? Is it because the alternator is abrubtly stopping and the computer is still polling for it ?

__________________
What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

The only difference you noticed might have been the battery light, but the extra wear and tear on the belt, tensioner arm, shock absorber, and spring are there too

-J

Jarod: As Engatwork said, the '95 606's came with a solid pulley. You could retrofit an OAP, but it's probably not necessary. (My '95 is fine without one.) Just make sure that everything else in the system is in good condition.

Funola: I'm not proclaiming myself an expert in this subject area, but the mangled pulley pins and self-loosening pulleys *could* be associated, but it's difficult to say. The consensus seems to be that V-belt systems can absorb/dampen a lot of torsional issues... but every system has its limits. Maybe a big alternator is pushing those boundaries. (?)

Greazzer: I think that VT220D is right; OAP's came along in the mid-90's. I don't know of any V-belt type pulleys incorporating a one-way clutch, but that doesn't mean they aren't possibly out there. The other thing to keep in mind is that these pulleys seem to be developed for specific applications. It's hard to see where a one-way clutch (OAP) could be too much different from any other, but the decoupler (OAD) pulleys have that torsional spring incorporated into them. That spring may be calibrated for specific applications, i.e., torsional resistance and travel may be very application specific. (I'm saying that hypothetically, not as a fact.)

Biopete: Glad this thread was helpful. Good thing it wasn't at high engine speeds when it let go... that could have gotten ugly.

__________________
Current rolling stock:
2001 E55 183,000+ Newest member of the fleet.
2002 E320 83,000 - The "cream-puff"!
1992 500E 217,000+
1995 E300D 412,000+
1998 E300D 155,000+
2001 E320 227,000+
2001 E320 Wagon, 177,000+

Prior MBZ’s:
1952 220 Cab A
1966 300SE
1971 280SE
1973 350SLC (euro)
1980 450SLC
1980 450SLC (#2)
1978 450SLC 5.0
1984 300D ~243,000 & fondly remembered
1993 500E - sorely missed.
1975 VW Scirocco w/ slightly de-tuned Super-Vee engine - Sold after 30+ years.

You can pick up the special tool needed to change the over speed pulley thru NAPA.

__________________
Jim

Dodge diesels with a serp belt and spring tensioner chirp as well though I chalk it up to the cooling fan. It comes from the motor bouncing back against compression and the tensioner being pulled. The slack side now becomes the tension side as the motor turns slightly in reverse, the tension side becomes slack allowing the still rotating accessories to slip.

So far:
Besides the Mercedes branded #604 150 03 60 Clutched Pulley [$120.51]
and it's companion cover #000 155 09 02 [$6.20] for the Later OM606

The Only other choices are a Gates Import and re-branding/packaging of
INA's version of the same Clutched Pulley (OEM type)
# 37011P [$82.79]
and it's installation tool # 91024-1 [$29.79]
Both available from Automobili Stone (anagram?)

Gates in Denver couldn't find any crosses for a DeCoupler torsion spring
pulley (The Obvious first choice,as it's providing more "Cushioning") in
it's system.

Gates did say that many of the Preferred DeCoupler pulleys were in use
in Europe (O.E. type).
And even went so far as to say some may be in use by MB in Europe.

An Independent Alternator shop [TAE] in Arizona told me they've seen
DeCoupler (Torsion Spring-ed) Pulleys on dead Alternators (from Europe)
sent in for rebuilding.
And when they contacted the O.E. automobile manufacturers,
(To be able to acquire New clutches for their rebuild customers.)
the Manufacturers USA representatives claimed that they didn't use them.
[So,there is some kind of "Disconnect" here in the Information Stream]

Both Gates and TAE told me that the Clutched Pulleys usually lasted
50 to 60K miles [And has been earlier stated by others here]
SHOULD Be considered a Maintenance Item.
(The DeCoupler Pulleys MAY last a little Longer,due to the engineering.)

When the Pulleys "Fail" it is a Catastrophic Event,for the Pulley.
In other words they are not repairable,ONLY replaceable.
(Metallic Swarf all over the insides of the Pulley)

There is some concern about "Beyond Junk" PRC Counterfeit "KnockOffs"
So, Be Forewarned!

_______________________________________________________________

All that said... If I can locate one of the DeCoupler T.S. type pulleys that
will fit the 143 Amp Bosch 0 123 510 021/Mercedes 009 154 67 02 alternator
that I upgraded the 124.128 to I'm all over it "like White on Rice".

The INA clutched Pulley is a valid second choice.

'Given the Mercedes (Overly Engineered/Complicated/Uber Expensive) Belt
Drive Tension-ing system.Along with the Potential cost and Angst of a
Timing Cover replacement.

One final thought,on the Positive column for Over-Running Pulleys...
Less Stress on the Crankshaft's Harmonic Balancer.

__________________
'84 300SD sold
124.128

If I am not mistaken, I believe that INA is the OEM supplier to Mercedes, but I could be wrong. I put an INA on my car, so maybe I'm just trying to distort reality to fit my actions. If you can't find an OAD that fits your specific needs, the OAP's seem to do an adequate job for our applications. BUT if you do find an OAD that fits, please let us know in this thread! (Nice shenanigram BTW.)

Good to know. Is that for a rental / borrowing program, or strictly for purchase?

__________________
Current rolling stock:
2001 E55 183,000+ Newest member of the fleet.
2002 E320 83,000 - The "cream-puff"!
1992 500E 217,000+
1995 E300D 412,000+
1998 E300D 155,000+
2001 E320 227,000+
2001 E320 Wagon, 177,000+

Prior MBZ’s:
1952 220 Cab A
1966 300SE
1971 280SE
1973 350SLC (euro)
1980 450SLC
1980 450SLC (#2)
1978 450SLC 5.0
1984 300D ~243,000 & fondly remembered
1993 500E - sorely missed.
1975 VW Scirocco w/ slightly de-tuned Super-Vee engine - Sold after 30+ years.

The tool isn't expensive on Amazon.

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Purchase from NAPA.

__________________
Jim

Poop ... My custom crank pulley should be done soon pretty soon and this thread made the concept even better. I will contact ASP Racing and see what they have to day.

What's of the concept of your custom pulley? What material is it made from and why do you need custom?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Runningtoohot: my 95 does indeed have the solid pulley.

I have little knowledge of what has been replaced on this car, but I've changed the tensioner shock, power steering pump (it broke off), and the a.c. compressor was replaced at some point.

The belt vibrates badly. At idle you can hear it from outside the car. Ill take a video when I get home from work.

Will the gates 37011p fit my alternator? I'd like to try one on her.

__________________
1982 300D (w123, "Grey Car")
1982 300D (w123, "Blue Car")
2001 Ford F150 "Clifford" (The Big Red Truck)
1997 Dodge Ram 2500 12V Cummins
1996 Dodge Ram 2500 12V Cummins
Previous Vehicles:
1995 E300D, 1980 300SD, 1992 Buick Century, 2005 Saturn Ion

As of today (28 November) I found the Ina clutched pulley for a 1999 E300 at Import-ec for about $37, and the splined socket for installation at F C P Euro for about $7. It appears that my OM60x head bolt tool 601 580 00 1000 is the right size to work with the socket (XZN M10) so I can avoid purchasing the Hazet tool kit for $47.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC