Timing chain? Tensioner?? Maybe not pumping up right away, allowing the chain slap, then once pumped up, tensioning the chain and quieting the slap? Just a guess.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.