R56 Knocking

[vpr]

From the top of the engine on a cooper S

Sounds like a diesel and if I take the oil filler cap off the noise increases making it obvious it's coming from within

The noise reminds me of an old cortina with a shot Cam

Any thoughts?

[rigga]

Slapping cam chain with possible broken guides would be a guess.

[vpr]

Yeah I've heard theyre an issue but thought that would be more of a rattle?

[RS250_Steve]

They sound terrible when they fail.
If one of the guides snap, especially the guide between the cam sprockets they sound like it's the end of the world.