Hello, I have searched many forums for an answer to my problem, I need help with. I was driving on the highway and lost my power steering, alternator and water pump(temp. climbing)pulled it over and found the crank pulley as well as all other pully's not turning (obviously). I took the car home after it cooled down for a few hours to have a look. I took off the rad a\c condensor, belts and fan/pulley. After the belts came off the harmonic damper/ main pulley assembly pretty much fell off. The large bolt (27mm) was broken with some still remaining in the crank. I drilled a hole in the stub of the broken bolt and used an easy out to get this out. The shear pins were destroyed and embedded in the crank snout and inside diameter of the damper plate. I flicked the small broken pieces out of the crank snout and took the damper plate to the local mercedes guys. I spoke to the local mercedes guys which advised me to change the front crank seal and thrust washer behind the seal as well as I showed them the inside diameter of the harmonic damper plate. They asked how the crank looked which I thought was fine. They advised me to get a new damper plate and ordered me some new shear pins and large bolt. They also put me in touch with a guy they Knew had another engine with a used damper plate to which I acquired. I took the damper off the donor motor complete with the shear pins kind of still lodged in the grooves of the inside diameter. and put it all back together. Because the old shear pins were nicely stuck in the donor damper I left them there and reused them. Everything went fine compared to some stories I have read about aligning the slots. I think this was in part because the wedged in pins made for a good way to guide the damper on. I used the donor damper bolt to cinch the new damper on to my engine and took it out periodically to check how things were going. When I could no longer get the bolt any tighter I took it out and noticed that the flange was not quite flush with the crank snout. maybe a sixteenth of an inch from flush. I also noticed that I had slightly stretched the threads on this older large graded 10.9 bolt. I used a fourteen inch breaker bar to tighten so I figured that had to be at least 300 foot pounds to be able to stretch that bolt. I was not too worried about the little bit out of flush on the crank snout and put in a brand new bolt with blue locktight. I tightened it as much as I could by hand since it had already appeared that I am strong enough to stretch threads and gave it a little more to maybe take the damper plate to flush with the crank... Even if it did'nt go I had the locktight on and a very strange new washer they sent with the new bolt. I am assuming this one piece tapered washer is a revision to the three washer set-up from factory.
It lasted a week and I am now in the same place I started... stripped damper plate and sheared off pins. The large bolt did not break this time but the blue locktight I put on seemed to come out of the cranksnout in large powdery chunks.
My question is where did I go wrong? The crank can't be worn too much as I had to suck the replacement damper on with a bolt.. it was a tight fit. Did I not get it on far enough? Do I actually need to get a torque wrench. I don't think I could get this bolt any tighter without breaking it. I could feel the breaker bar flexing. Do I need to use the new pins (ANODIZED YELLOW) that I got instead of the older ones from the donor car? Now that this has happened again do I need to change the crank seal and thrust washer again? It looks O.K. Thank You for your time and response and please don't tell me to get a new engine as this one runs like brand new except for the damper problem. Why would Mercedes have such a stupid design for an otherwise good engine? Square shear pins on a small block chevy crank are looking like a way better idea. I have never heard of one of those coming off. Could this be indicating another problem, I don't think so... this motor was / is still running great..