My car overheats when I got stuck in traffic so I guess I need to replace the thermostat, water pump and also at the same time the upper and lower radiator hoses.

Last time I heard the engine made noises I looked by the pulley and the pulley in front of the water pump wobbled. does this wobble caused by weak / bad water pump? Do you think I need a new pulley? Again there is no leak on water pump unless if it is small and unnoticeable.

Anyway I will replace the pulley and the serpentine / v - belt too because uneven contacts with pulley might damage it.

 

Reading your post correctly: The bearing that can cause the pulley to wobble is inside the water pump.
So, change the water pump before changing anything else.

 

Will do, thanks much kraut56 you answered my question, but the genuine water pump pulley and the v belt last time I checked from mymercedesparts.com only cost me, if I remember correctly, $48 and $20. Sp good investment to throw those in too.

 

Not much that can go wrong in a short time with a properly-installed water pump pulley. I would check it before replacing.

 

Replacing the v belt and pulley will require that you remove the upper radiator hose (drain coolant first) so that you can remove the electric fan.

With the v belt off, and the pulley exposed, you should be able to determine if your wobble is in the pulley or the pump itself. The pump isn't cheap...

 

Thanks for the answer Astro14, Wallyp. I am not mechanically inclined but would like to know what is wrong so I could get the right parts and have the indie do the work as needed - so I don't run to other problem in the near future.

So by any chance with 118k on the car do you think it will be good idea to replace the crank / harmonic balancer / vibration damper pulley as well? Fyi, the idler pulley replaced at 96k.

I got the Bosch water pump for $199.

 

I've only owned this car for 6 months...so, my experience with the MB M275 engine is pretty limited...

I replace tensioners when I replace belts, especially timing belts, and serpentine belts like this one that are a real PITA to get at....and I take a good look at the other pulleys for condition, play, free spinning (no grinding/resistance) while I am in there...

But, I've only replaced one harmonic balancer in my life (which includes ownership of over 20 cars) and that was on a 200,000 mile Oldsmobile V-8 from the 70s...so, I wouldn't suspect a problem with that component.

 

Thank much for the info, one more less thing to be concerned about.

 

This is a pretty unusual failure on most vehicles. It does happen occasionally, but I doubt that it is worth buying one in advance, or replacing it "just in case".