ytech15, some of the noise on cold start is the air pump. The engine sounds "normal" most of the time, but the loud bursts sound threatening. With a bad timing chain tensioner, likely the result of a broken internal spring that fails to keep the timing chain tight at start-up, you will hear the timing chain slap until oil pressure builds up inside the tensioner. Best to have a MB-trained tech familiar with that vintage engine diagnose the problem before your engine suffers potentially serious damage. I had the timing chain tensioner replaced in the M104 engine in our 1992 300CE around 100,000 miles. I always run Mobil 1 15W50 in our vehicles with that vintage engine (1995 and earlier).

__________________
Fred Hoelzle