Oil Pump Noise

[MotoSook]

I listened to an engine today that had an extra mechanical noise to the usual flat six noises. Using a metal rod to my ear, I pin pointed the noise to it's strongest point. It appears to be stongest when I put the rod at the drain plug. Along the case seam, the noise starts to die off as I move away from the sump cover.

It didn't sound like a rod knock and the noise did not got louder with increased RPM. It was loudest at idle, then it was masked by the engine noise at higher RPM.

It was sort of like a chug chug noise (almost like a diesel in the back ground but a low tone to the diesal noise), but low tone and mechanical. It was not that loud, but I could tell there was an extra noise to the usual noises. The owner never even noticed it until I pointed it out and let him listen to my car.

So! Could a worn oil pump sound like that? Pump vanes with too much clearance?

The engine sounded healthy otherwise.


EDIT: Engine has good oil pressure (close to 1 bar at idle, and relatively warm). Engine is a 3.0 SC. Engine pulls strong.