Knowing very little about enerpac pumps, I'll speculate in general about hydraulic pumps. Anything leaking or wrong with the pressure side would be obvious at 10,000 PSI. Unless it was the relief valve, but that's adjustable, easy to inspect, and would build heat if it was leaking, in addition to causing pressure loss. Air in the system would by design be cleared after a couple of cycles with no load. The only way you could be getting air is a suction leak (don't know if that's possible of if the pump is submerged in oil), or the oil is foaming. Either one could make a wicked noise at that pressure, and explain the smell. Air in that system could diesel, making the smell even worse. Of course there's always the possibility of mechanical problems like a coupling slipping or a bearing seizing up, I'd think those are less likely to make the smell, but if they did they'd be easier to find than the smell coming from the hydraulic reservoir.