1999 ML320, 193k - I just inherited this vehicle, and it sounds like a diesel with all the noise coming from the valves maybe - too noisy for it to be lifters I have been told.
Previously, a lubricant stopped the noise for a while but it came back.
Any ideas? Thanks

drive belts can fool you,A 320 was know for harmonic damper problems,Light weight motor oil may need to use 15w40 oil.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

I had a reply about another issue that may be the culprit:

JamesComments: 1999 ML320 - I just inherited this vehicle, and it sounds like a diesel with all the noise coming from the valves maybe - too noisy for it to be lifters.
Anyway, I changed the oil today and attempted to put a quart of Lucas Oil Stabilizer down the oil filter housing and it would not drain down. I let it sit for about an hour and there was still fluid standing in the housing about 2" up. I then put 7 qts of oil in the oil filler opening and put the filter back in the standing oil in the housing.
Also, when I removed the old filter there was no oil, to speak of, dripping from it - but the dip stick read full, and I had just driven around to warm up the oil as you suggested. Also, there was no long spike at the bottom of the oil filter like your picture shows.
This doesn't sound good, but I was hoping it might be an easy diagnosis.
Thank you, JamesAugust 21, 2013 Followup from the Pelican Staff: After you started the engine and shut if off do you get only in the filter housing then? You probably have a lot of sludge built up in the valve cover baffling that is blocking the oil stabilizer from draining into the motor. You may need to pull off a valve cover to look at how much sludge has developed. - Kerry at Pelican Parts

If there is sludge blocking the port to the oil filter, is there something I could pour down the oil filter housing to dissolve it?