I have encountered a number of radial seals which needed to be replaced and or lubricated due to a high pitched squealing noise (AKA-Whistle). I have replaced numerous M116 and M117 water pumps that poured coolant onto the crankshaft hub which essentially causes the crankshaft seal to dry out. After having to replace a few crankshaft seals after replacing the water pump I began to lubricate the front crank seal during the water pump repair.

In this instance perhaps the outer radial seal(s) on the water pump shaft was a bit dry causing an unusual noise. A little lubrication quieted the noise, for now. I do imagine the water pump [AKA: Gravy Pump] will need replacing soon….it's just a question of time.