The crankshaft broke after the water pump was replaced. It would appear the sequence is - water found to be leaking - new water pump installed - crankshaft breaks. This would suggest the water pump replacement isn't doing its job, whatever that is and caused the engine
oil to burn and become solid then the crankshaft broke. If this is so we can surely claim against Mercedes. The original pump has lasted 175000 miles so why should a new one suddenly not be up to doing its job?
Nick van Rensburg