Strange Engine Noise, Tick -2002 ML320
 

Wife’s 2002 ML320, hopefully link to video below works.

https://share.icloud.com/photos/09ppqPCKEbFctunj3x9CMS-_g#Forest_Acres,_SC

A little background. 147,000 miles, Was purchased new by my mother in 2002. All maintenance performed by local Mercedes dealership until I received the vehicle in 2016. Since then I have maintained vehicle with the exception of having both catalytic converters replaced a few months ago by Midas (I knew having them replace the converters instead of a qualified independent was probably a mistake, and was I right).

Knew at least one of the cats was clogged but vehicle still ran well and no check engine light. Wife called me one day and said engine died while traveling down interstate. Had vehicle towed home. Researched and felt reasonably certain in my diagnosis.

Priced several different places and Midas was the lowest and they could get the car in and out the quickest. Knew I was probably making mistake, but wife couldn’t be car-less for more than a few days and my thought process was I wanted to sink as little money as possible into this as these W163s really aren’t worth very much in today’s market.

Midas called back after one day said it wasn’t converters, it needed a tune up. I was surprised but said ok. I took correct plugs and wires to them (had recently purchased for a planned tune up) and they said it should be ready the next day. Called me the next day and said after tune up, car wouldn’t go more than 30mph and after further investigation, IT WAS BOTH CONVERTERS that were bad.

They apologized, and said there would be no charge for the tuneup.

Took them 3 more days to order cats, get them in, and install them.

Ended up costing me about what it would have cost at a highly recommended Mercedes independent shop.

Expensive lessened learned.

Car does run cooler, fuel mileage improved, and is much quicker. Didn’t realize how much performance was being lost due to clogged cats.

When got car back, was making the noise heard in video. Thought possibly just needed oil change, was due. Noise still there (run full synthetic oil).

Noise has not gotten worse or improved. My initial thoughts were Midas mixed up plug wires after tune up but they all seem to be in the correct location.

Hopefully it is something simple but probably not with my luck. Any thoughts or suggestions are much appreciated.

Thanks. -Scott

noise
 

Remove the intake manifold and check your flaps they may be broken causing knocking noise, there are shafts and flaps inside

Kind of hard to tell from the sound on a video...
But sometimes a misfire/ jumping spark makes a ticking noise.
Possible those knuckleheads messed one of the wires during the tune-up.
You can visualize a misfire sometimes if you look at the area in pitch black dark.
Maybe since it has two plugs per cylinder, performance isn’t affected? I’d think it would throw a misfire cel though.
Could be something else

Does it make the noise cold , if not it may be excessive carbon buidup causing the piston top loaded with carbon to hit the head , i had one m 112 do that once head was removed was able to measure 035 buidup of carbon on the head and 035 on the piston, try a can of carbon remover , bg makes an excellent product , removing carbon fixed the knocking noise