The pump that pressurizes the hydraulic system is at the front of the engine, towards the driver's side. It's a round radial-piston type pump. There is a flange and a gasket between the pump and the engine block and when the gasket goes south, the pump will leak INTERNALLY. If one of the pressure hoses is bad at the pump, it will leak EXTERNALLY. Make sure this is in fact hydraulic fluid that you're seeing because it's not uncommon for the pumps to leak internally. This will then cause hydraulic oil to be sucked into the engine oil circuit.

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Regards,
Aaron