I am working on a Valmet( now Komastsu) 445exl. This machine has a three pad pump drive. One of the pumps is leaking hydraulic oil into the gear box and over filling it. All hydraulic function on the operate as normal. So I think it is likely just a pump shaft seal, but which one? I was thinking about making a pressure regulated device to force air into the case drain port of eachpump to determine which pump is the leaker. How much pressure ? Without blowing the any good shaft seal out. Thanks
Not familiar with your machine - so don’t know what pumps are there. Shaft seal leak in the oil filled drive means one of or both - high case drain pressure and/or failing shaft bearing, for piston pumps. So to not to have frustration on your hand I would suggest taking all three off and inspecti the shafts end plays and case drains all the way to the tank. Also for piston pumps usually the highest safe case drain pressure is around 50 psi. That said, it would REALLY be smart to ID the pumps and look up max. Case drain pressures in the manuals for them.
Sometimes just separating the pump from the drive will identify the culprit.