Well I hate to say it but I have accepted replacing the harmonic balancer on 112-113 engines as preventive maintenance. Its way easier and cheaper than replacing the upper oil pan or the front timing cover. A new balancer is about $80.00
I have seen both old and new styles fail, and closely inspect all balancers on these motors. I have never seen one on an AMG car fail, and the 113 failures appear far less common than the 112 failures. Check for rubber poking out at one spot farther than anywhere else, 1-2 mm is enough for me to replace it. Any cracks, wobbling, or just gut instinct. Some go over 100K and still appear fine, I have replaced a new style balancer after just 3K miles of service due to rubber poking out. Do not toy around with balancers! They will burn you hard when they let go, and roughly $300 is cheap insurance against an oil pan replacement and all the potential problems that creates as far as oil leakage. It is rather difficult to replace an oil pan, and trying to keep it clean while installing it is very tricky. Even letting them drip overnight doesn't help much.