KNOCKING NOISE. please help
 

recently purchased a GT TDI 150 2003 off my brother, car been off road for 3 months, was fine for a day but now when i start the engine, there is a loud knocking noise from inside the engine, sounds like it coming from in the engine on the drivers side. its like every 5 seconds `knock,knock` like a crunching sounds, really unhealthy noise. It seems to go quiet when i press down on the clutch. Also once car is heated up its fine, and if i restart car a hour or so later its fine aswell. Just when left over-night from cold start. car running fine and not overheating or anything....camblet also replaced 3 years ago....


any ideas?