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).

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Fred Hoelzle

Thanks for your input.
I'm planning to replace the drive belt tensioner, shock and adjustment road soon, It does not seem too hard to replace the timing chain tensioner while doing this job BUT I'm afraid that the chain will jump a link with no tension (while the tensioner is out, 99K Miles. didn't take the valve cover off so condition of chain is unknown.. ) .. what were the symptoms that made you replace your tensioner?
also, are there any kind of oil additives that can actually help revive the lifters?

ytech15, the 104 engine in our 1992 300CE had a disconcerting, abnormal noise at idle. A local indie told me not to worry about the noise; however, an experienced tech at our local MB dealer diagnosed the problem as a failing timing chain tensioner. A new timing chain tensioner (installed at the dealership) resolved the problem. As far replacing the tensioner yourself, it's critical to maintain the timing marks with the camshaft. If you decide on DIY, be sure to have detailed MB instructions that you follow exactly. Otherwise you could end up destroying the engine. I doubt that your timing chain would need replacement, but you should check for any stretch. Typically the timing chain guides need replacement on older, high mileage engines.

Mobil 1, as well as other high quality, oil has additives that keep the engine clean. As you probably realize, hydraulic lifters rely on oil pressure to keep them tight against the camshaft so they are quiet. Routine oil and filter changes with a high quality oil will extend engine life. If your engine has been neglected, it's possible you need to replace the hydraulic lifters. I have put 200,000 miles on a 104 engine without the need for any major engine work.

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Fred Hoelzle

Finding dealer techs that actually have any knowledge regarding pre OBD II cars is an impossible mission, at least at the dealer by me (south jersey philadelphia area, that’s enough to figure out which dealership I’m talking about). I do have the detailed instructions regarding the tensioner replacement (which have no mention of the cam marks) and the tensioner is pretty inexpensive, which makes the replacement easy BUT the more research I do indicates that failure of timing tensioner will lead to constant rattle especially when hot.
The fact that an oil change has started this issue is driving me crazy.
I’m seeking for some more advice and options here.
Attached are some TSBs that I found.
Please continue to help me !

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ytech15, call Mike Strickland (Service Director at MB of West Chester) at 484-313-1111 and ask if there are any techs still working there that are intimately familiar with the M104 engines. My timing chain tensioner diagnosis was at least 12 years ago so those skilled techs may be retired now.

Our M104 engine had a "slapping sound" with a slight RPM increase above idle. The more I think about it, due to the timing chain tensioner not building up enough oil pressure to keep the timing chain taut.

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Fred Hoelzle

Thank You. I will give him a call on monday..
Just so I’ll be able to establish a better understanding. will you say (from the video) that I have this slapping sound?, also, was this slapping sound present at all times?