97 W210 Screechy/ tappy sound at start up 2-10 seconds
 

did some searching first but couldn't find anything. Thanks for the help in advanced!

(NOTE: It sounds like valves but I could be wrong since I am in the car when starting and not under the hood)

Tappy sound is normal for M112, just the lifters tapping till they pressurize...all of the ones we have do it for a couple seconds on cold start. Screeching is probably a worn belt/tensioner or dragging accessory like the P/S pump or alternator.

Thank you Pawo, I just got the car a month ago, it didn't do this sound for the first 2 weeks, so its a new sound to me, that's why I was concerned.

M112??

Im pretty sure the 112 engine was a 1998 deal - this 97 should have the old M104 straight six engine. Eitherway the tappy sound at cold is lifter noise, use good synthetic lube in the engine and get it to operating temperature then beat the engine once or twice a week (rev hard) - I used to have the ugly tappy sound and it went away after 2 oil changes (took a darn long time tho) - 10,000 miles per change (M112 V6 engine in my car)

Yup, in line 6! Ill try that and see. thank you

The fan belt might be slipping. After cranking the engine, the battery needs to be recharged increasing the load on the belt. Also, the M104 for that year will an electric AIR ( emissions ) pump. This adds a large electrical load and might even be making noise on it's own.

Where is the AIR (emissions pump) Located?

Just below the alternator

Well, turns out, my radiator fan is touching the radiator at the bottom. Any ideas why this would have suddenly gotten misaligned?

The plastic shroud could have slipped down when someone tried to re-attach it with spring clips. Two at the top. The radiator is also spring clips at top, fits in a groove at bottom. Exam each and every fan blade tip, if one is partially snapped off will increase wear on other parts.

I also recently bought a high miles 91 300TE, was sounding good. I had oil changed and a new Mann filter, used Shell Rotella 15W40. Drove 15 miles and parked it. Next morning made a clattering noise for several seconds, which went away. I took this to be the chain tensioner. Added Marvel Mystery Oil and have not heard that noise again, even though it has been 14F where I park. I will burn a chicken to honor the sludge removal formulators and snake oil sales weasels.