I am talking about my Euro spec 1984 300D with a normally aspirated (non-turbo) 617 motor. A few months ago the front pulleys and vibration dampener fell off when I was driving about 70mph. I shut the car down real quick and pulled to the side of the road. Broke my fan, and the flying broken fan blades shredded the radiator. The car didn't overheat, unless you count the retained heat after losing most of the coolant.

To be clear, I am trying to stick to Mercedes terminology: the vibration damper is the piece that looks kind of like a brake rotor, it is sandwiched between the lower pulleys and what Mercedes calls the balance plate. The balance plate is held on to the crank with a big center bolt and two dowel pins.

No problems with the balance plate attached directly to the crank, it stayed solidly in place. The six bolts which go through the lower pulleys and the vibration damper sheared off.

The vibration damper and pulleys stayed together (rust) and remained in the engine compartment, the belts kind of held them up. I had the car towed home, and when I took the vibration dampener/pulleys loose from the belts and out of the car, a few of the bolts fell out of the middle of the pulley. some of the bolts were sheared, one was full length but mangled.
The vibration damper itself looked pretty bad to me, all 6 bolt holes were ovaled, some more than others, the bolt holes also showed thread marks, like the disk was wobbling loose for a little while before it came off.

My running 240D was out of order with a busted axle, and I had a another 300D parts car sitting, so I figured I could swap the vibration damper from one 617 motor to another 617. Not necessarily so! The vibration damper disk that fell off of my 1984 Euro spec, non-turbo 617 turned out to be thicker and more deeply “dished” compared to the damper that I took off my 1982 US spec, turbo 617.

The crucial difference between the two is the depth: the bolts that held on the US turbo version were M8x_ , the bolts that held on the Euro non-turbo version were longer: M8x45. As well it’s more than a matter of just using longer bolts. The balancers are different, the US turbo vibration damper is not deep enough to seat down flush to the bottom of the recess in the center of the Euro balancer. If I were to cobble together a bolt length that “worked”, I’m sure that I would shear those bolts off very quickly.


More bad news, when researching the FSM and online I saw that The blts were supposed to be allen head cap screws. The remaining bolts that I found after losing the vibration damper/pulley from the motor were 8mm allen head but they weren’t cap screws, more of a round head.



I decided to get the old sheared off portions of the bolts out of the balancer plate, there were three stuck in there. I was able to just spin two out by catching the broken edge with a screwdriver. The third was stuck in there real good, I center punched it and tried to drill it with some pretty decent drill bits, really didn’t make a mark, just made it shinier.
I examined the old bolts and thought they looked a lot like stainless steel. I looked at the vibration dampener again and noticed what looked like some orange junkyard type markings. So I guess this isn”t the first time the vibration damper fell off the front of this motor.


I put the “original” vibration damper back on the motor, even though I had my doubts about it, and drove very carefully for the next three days until my new axle came for my 240D. The day after I parked The 300D I found half of one the bolts in the parking lot at my job. I thought that I might have over torqued one bolt when I was getting it together, I used a torque wrench and paid attention to the specs (35Nm) but I thought I felt one twist and give, the spot I was working had a lot of traffic noise making it hard to hear a click and the position I was in made it hard to feel the click.


I feel very fortunate to have made it through those three days without doing any further damage.


The question: is the difference in the vibration dampeners a Euro vs. US difference or a turbo vs. non turbo difference? Anybody ever take apart the front of a US non-turbo motor? Does the vibration dampener on the right look like the vibration dampener on a US non-turbo motor? If so I should be able to find a part fairly easily that will fit.


Anyone ever take apart a Euro spec non-turbo? Does the vibration dampener on the right look correct? Because with the stainless steel non standard screws being used, I do have to wonder if this is the correct part for the motor or if it’s just something the previous owner thought would work.


I am optimistic that a US non-turbo 617 may have the same vibration damper as my Euro 1984 non turbo 617. The one shown in this Ebay listing looks similar.



Mercedes W123 OM617 Non Turbo Harmonic Balancer | eBay