squealing noise when releasing throttle
 

i have a 2005 w203 c200 cdi, with 80k on the clock.
lately i noticed that when i start it up in the morning and drive off, i get a squeal when i release the throttle. it doesnt do it under load, it does it only when releasing the throttle. then after about 15 mins it goes away.
it does it also when i switch off the engine when its still cold.
my mechanic told me that its still too faint to tell, and that i should ignore it for now and wait till the noise gets louder, but he reckons it might be the turbo.
what's puzzling him though is why it stops doing that noise after a while.
any ideas please?

I'm no expert, however perhaps you should check the power steering pump and all the belts for tension and overall condition. Does the squealing noise happen when you turn the steering wheel after starting the car?

i use Fuchs Titan GT1 5W-40 synthetic oil.
the noise happens even with the steering wheel straight, it doesnt make any difference.
it happens when the car is not fully up tho temperature, when im accelerating and then release the throttle, there's a fine squeal, it last a few seconds each time, i guess maybe till the turbo stops spinning, but im not sure

If it were your turbo as you suggest, the effects on the turbo would get worse after it heats up. Not better. Bearings get hotter as the turbo spins ups. If it were the turbo, you would definitely feels the loss of power or lack of power. I would double check all your belts for slippage. It's cheaper to do than focusing on the turbo and simple to isolate. If the belts are checked, replaced (assuming they've never been replaced), I guess you can focus on the turbo. Bearings are most likely the problem with turbos, oil coking.

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thanks SINAPE62, i will do just that.
nexrt week i will go to my mechanic and tell him to change the belts, we'll start from there and see how it goes.
if it was the turbo, do you know if there is a cartridge replacement where you could just replace the fins, or is it a whole turbo you have to replace?