I have a 1991 Mercedes 420SEL and I'm stumped about how the crank pulley and harmonic dampener can come loose (last week --the pulley moved forward and was flopping around, cutting into the fan blades -- dampener totally loose). Isn't there a big 27mm bolt and other smaller bolts holding all this in place?? Am I missing something???

I'm an aviation mechanic, and I can do basic work on my car. I just had the situation repaired, but I don't understand how it all came apart.... any explanation would be greatly appreciated...

Thanks!!
Bob Irving
Charlotte, NC