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Imagine this AOP has poor initial engagement when engine first started and then it catches up and all OK.
I personally never own AOP pulley, so I am guessing. My M276.820 does not get AOP pulley, but yours is a C207 chassis, albeit same engine as mine if E400, may get one who knows.
Jetta wrote in that thread : Interesting. My 2015 SL400 with the M276.8xx engine has a solid pulley, while my 2014 C350 with the M276.9xx engine has what appears to be an OAP pulley based on the style of the cover.
W207 E400 333ps. Ex R171 SLK280, Ex W211 E500, Ex W209 CLK500.
Thanks, Prihadi. That's a good lead...
Mine has blue efficiency crap (start/stop, etc.) and according to the online catalogue my pulley is A2781500060 which seems not to be solid.
If I understand correctly, this makes the alternator axle to be able to turn free when it goes faster, for example, if the engine stops suddenly or if electrical load is removed. Don't know if something can happen / engage during cold start-up that may change so the noise is normal for a couple of seconds and then starts making noise.
If only I could easily disconnect my V-belt as I could in my good old M113...
Will try to see how accessible it is (I am afraid it is not too much, due to the front intercooler stuff).
Yep, the P/N you mentioned, it is AOP pulley.
Wow, the way MB uses this pulley is so odd, it is not based on engine alone. There are more M276.8xx getting this AOP pulley, example on GL450 according to FCP Euro.
yep aftercooler must be removed to access the serpentine belt for removal , otherwise you can't loop the belt to the water pump pulley and main pulley
.
If you are in there, best to replace the 2 plastic pulleys and the tensioner.
I already did mine and I am only at 36,000KM or so at that time.
W207 E400 333ps. Ex R171 SLK280, Ex W211 E500, Ex W209 CLK500.
Hi,
I just checked and my alternator pulley looks like a normal one, with a big nut in the center. I could discard that.
Maybe the A/C compressor activates a couple of seconds after power up and its bearing is bad? I will try and check.
Also, do you know if there is any SAI pump as in the M112/113/M272 engines which starts when cold for some seconds that could be noisy? To me it doesn't sound like that, but the fact that the rattling noise doesn't start right after firing up the engine really puzzles me and I wonder if there is something I can try and disconnect.
I already tried with the turbo control valve, I didnt' notice anything pulling the vacuum or even forcing it during start up.
Best you lift up the car with all under carriage panels removed, and do cold start and find the noise source/proximity, otherwise it is tough.
Our AC is variable volume, it ramps up pressure slowly, but I doubt u turn ON ur AC during cold start...right ?
W207 E400 333ps. Ex R171 SLK280, Ex W211 E500, Ex W209 CLK500.
Yes, it is indeed difficult, plus I don't have an elevator at home... Will continue investigating. If you happen to think about something that could cause these curious sequence, just let me know!
Thanks!
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, otherwise you can't loop the belt to the water pump pulley and main pulley
