carlosrx7

Hi everyone, new to this forums and first post. Be gentle, as there are many threads about knocling sounds on this engine a new one may be repeat but cant find one that can answer my doubts. I love to find a repair issues to cars, specially difficult ones, but this is confusing me. I got an offer for a 2010 c300 with 74000 miles thats looks really good at a very low price, but this car have a very hard knocking sound at low rpms, I know the fatal story on m272 engines with the camshaft balance to go bad due a low quality materials used by mercedes, and my first guess was that the knocking sound comes from this defect. But by this year on the car as far I know was corrected by mercedes so probabilities goes down but not 100 percent. I research a little and read about an O ring inside the oil pan with the oil pump that goes bad and make a sound that may be confused with a timing chain problem, so here start my confussion. Today I was able to see the car. It start at the first try, the noise is loud but as rpms increase about 2500 to 3000 rpms the noise is gone completely no vibration in the end looks healthy. I saw some vibration on the engine also at low rpms with the noise, in another search someone claim that have a similar problem, vibration and knocking and state to find a bad coil, after replace, knocking and vibration is gone. Notice an intake hose, one of the two running to the front of the car have a perforation, dont know if this affect, Also notice some work on idler pulleys, new computer and owner claim recent oil change. Owner claims knocking dissapears at 40 mph. I dont drive the car to avoid more damage specially if is relationed with timing problem. Dont know the oil and filter used in the last change, hope is the right one, specially the filter as also in my research, improper oil or not original filter may cause issues like engine knocking noise. Notice no engine light on, but also never comes on as I put the key in the on position, so there is a red flag for me, damn I just forgot to take my code scanner today, cant post codes if any. My most concern and confussion is that m272 engine with the balance shaft problem the knocking dessapears or is continues no matter rpms
? This problem could be oil pressure problem? or
anyone have similar problem that have been resolve and what was the issue? Sound posted for reference. Hope to someone give some light to this problem.

Thanks is advance