Finding a Strange Ticking Noise in an Alternator

If you don't look closely this one can be hard to find!

I pulled into a drive through the other night on my way home and heard this loud clinking sound in the engine. It was so loud I had to shut to engine off to place my order. When I got home the noise was gone. Next day noise showed up again but would "come and go."

Problem & Solution

Common among these chassis:

W115
W116
W123
W124
W126
W201

This one was hard to find, but when I noticed some damage on the cooling blades of my alternator fan I knew I was getting close... but what could have dropped into those blades? Upon close inspection I discovered one of the main body screws of the alternator had backed out and the screw head was hitting the fan. The other three screws were loose as well. Look below at the one that was bent!  Pulled them all out and applied thread locker and re-tightened. Wow, can you imagine what would have happened if all the screws would have backed out on a long road trip?