Check the right side of the timing chain cover to see if a worn chain has rubbed thru the cover & is leaking oil.
As to the noise, IF you have a lifter intermittently collapsing on an INTAKE valve this could be the "Thump" you describe. If the piston starts down on an intake stroke & the intake valve don't open at the proper time the piston will generate a higher than usual negative pressure, and when the valve does open late, the resulting rush of air will "Hit" the piston & cause a "Thump". This phenomenon is more prevalent on diesel engines with worn cam lobes than gasoline engines though.
What does the correct answer win?
