Has anyone had a hydraulic oil leak into the seed air flow from the fan? Our drill is a 2013 4m. I can only think the oil can be seeping past a seal in the fan. My main suspect shown in the parts book pages 204/5 would a gasket kit marked '12'. The 2 options in the parts list are for Bosch or Sauer pumps - mine has 'Rexroth' stamped on it. The fan is still working so I assume I don't need a whole new hydraulic pump.