Can anyone tell me if they think that this 550 sounds off?

 

What do you think is wrong with it?

 

Hard to say definitively from the video though it sounds “metallicy” - a new word! I would approach hesitantly.

Minimally, a mechanics stethoscope to pinpoint sources of concerning metal sounds.
I heard a worn bearing or equivalent of some kind (very precise I know) and timing chain chattering & possible high pressure fuel pump side cam chatter.

Realistically, the above plus if set on buying this X166 platform a dynamic compression test at a qualified Indy and post printout for group input, though results will be obvious me thinks.

For the group, also a good idea to state year, mileage, maintenance service record history. If it’s available & documented that’s a plus. VMI record available with sale?

Not sure if you own one already or are thinking of buying one for the first time - please also state for the group.

Note, these vehicles are maintenance intensive & I say this with years of work on one or three. If you’re independently wealthy you could pay folks to work on them, BUT…

It’s a great platform, but an onerous one. Current X166 has 224k miles and gets louder by the day but still moving. Lots of guidance and hard won knowledge leveraged from this forum to keep her going - thank you to the Forum as always .

All that said, if the mileage is really low with the price, and interior is in excellent condition, no cylinder #5 taking a , black coolant hard biodegradable plastic lines not leaking & intact, radiator has no witness drip lines on right front support at hood level, airmatic suspension system goes up/down through equipped ride heights, wiring harness not chewed on by critters, no wheel bearing groaning, tires in decent condition with less than 3 years from date of manufacture as read from within born on date 4 numbers within a circle on tire, rims straight & not hopping from pothole impacts, no front end nor rear end clunking when going over speed bump at 5 mph (emphasis), no pulsing of tranny when at hot operating temperature and at stop light after spirited test drive, no cracks in nor around flex bushing within driveline, no pulsing in brakes nor side to side vehicle movement following hard braking scenario (repeat 3X), no check engine light on (check & record odometer & have owner add another 100 miles or so to insure they just didn’t clear all the toggled codes), have Indy scan for codes (though see previous clearing of codes in prep for sale), telescoping steering wheel moves in/out no issues, heater blows HOT air (not tepidly warm air) after 10min drive time AND after 10 min on highest fan setting, both key fobs lock/unlock vehicle from distance, all door handle inductive locking sensors work and lock all doors, trunk opens/closes without issue, factory installed tow hitch wiring actually works with a brake controller to stop your trailer by actuating its brakes, alternator outputs between 13.9V-14.6V, both batteries changed out within the last 3-5 years, no timing chain clattering & banging like monkeys on a tin barrel - then I’d say it’s a good buy .

I have now passed the baton of years of working X166 platform knowledge consolidated into the above paragraph. And you though Mercedes Benz made a good product…

When all the above flushed out, it’s a great driving & safe vehicle for me & the family. But dang, seriously.