CLK 320 C208 Screeching/Screaming noise when letting off the accelerator

XC3113NT

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Hello everyone on this Mercedes Forum!

So it's my first post on this forum and so I don't really know if im doing this right, but anyways I figured I might try since I've got a problem with my CLK. It's a "99 CLK 320 my very first car. The milage is around 140 000 Km or roughly 87000 miles and somewhat regularly serviced, it's right now very overdue for an oil service if that plays a role in my problem. But my problem then is that when I let off the accelerator the car gradually starts "screaming/schreecing" a very unpleasant noise that really screams in your ears. And then it gradually gets quiet after a couple of seconds. It happens the most when it's hot outside I think. Now my parents have been in the car when the noise have been able to be heard and both of them don't think it's related to the accelerator and neither did the previous owner (my granddad). They instead think it's A/C related since they had described the problem to a very good mechanic and he said it was A/C related but had never listened to the problem himself. But I still think it's something related to the accelerator/engine or something just for the fact that it mainly arises when I let off the accelerator and it's hot outside. So if anyone have any suggestions i'm thankful for all of it and thanks beforehand.

Anyways if someone might know something and need more info please write it and I can see if I can get that info. And also if I posted this in the wrong segment or anything then please tell me that aswell. I'm thankful for all the help from anyone and now that I've got a Mercedes I'll probably be here quite a lot from now on.
 

Blobcat

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Hello and welcome

Is it the auxiliary belt, the tensioner, idler or one of the pulleys making the noise?

Does it still do it with the fan and heating off?

Dies it change note when you move the steering wheel?
 
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XC3113NT

XC3113NT

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Hello and welcome

Is it the auxiliary belt, the tensioner, idler or one of the pulleys making the noise?

Does it still do it with the fan and heating off?

Dies it change note when you move the steering wheel?
Hello

It does still make the noise with the fan and heating off and it could probably be the tensioner, idler or pulley that sounds, haven't really thought so far since it's gradually rising in volume when it makes the noise. But I will for sure look if it might be any of them. And about when I move the steering wheel I don't think it changes note, it's not something I've noticed but I don't think it does atleast. But if it would be any of the pulleys or the idler or the tensioner, then how would I notice that? Would there be some play in any of them or the belt being loose or what should I be looking for?

Thanks for your answer!
 

Blobcat

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You'd need to release the belt and feel for any play in the bearings. You can listen and watch with the bonnet open - just keep your fingers and any other appendages or loose clothing away from any moving parts - you might need to remove the plastic engine cover first (do that with the engine off)
 

Uncle Benz

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Does the noise disappear instantly if you apply the accelerator again? When you close the throttle the intake vacuum goes high, and you could get a screeching noise if there’s a vacuum leak. Plenty of places it could be, but the brake servo is one. Does the noise change if you apply the brakes?
 
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XC3113NT

XC3113NT

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You'd need to release the belt and feel for any play in the bearings. You can listen and watch with the bonnet open - just keep your fingers and any other appendages or loose clothing away from any moving parts - you might need to remove the plastic engine cover first (do that with the engine off)
Alright I'll go over that the next time I'll work on it, thank you so much for the help!
 
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XC3113NT

XC3113NT

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Does the noise disappear instantly if you apply the accelerator again? When you close the throttle the intake vacuum goes high, and you could get a screeching noise if there’s a vacuum leak. Plenty of places it could be, but the brake servo is one. Does the noise change if you apply the brakes?
Nope, the noise is determined to get as loud as it usually is no matter if I press the accelerator again or not. And pressing the brakes doesn't change it unfortunately.
 

mattkh

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Nope, the noise is determined to get as loud as it usually is no matter if I press the accelerator again or not. And pressing the brakes doesn't change it unfortunately.
If it only happens on a hot day, the chances are it could be the pulley of the aircon compressor.
 
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XC3113NT

XC3113NT

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Okay so I haven't been able to reply any today, but I have been able to go out and test it a little bit more and I might have been a little wrong.

So the noise is still present when I let off the accelerator, but as soon as I touch the accelerator just a little bit it gets quiet until I let off it again. But when testing it on idle and revving it in neutral a little bit I noticed that when it makes the noise and I turn the fan on a little bit, it immediately stops. And no matter how much fan I got on it won't make the noise atleast at idle, and with the EC button pressed (light on) the noise won't sound.

Sorry for the wrong information. But now I know for a fact atleast that the noise is present when I let off the gas with the fan and A/C off when I'm driving, and that it stops immediately when I switch on the fan or A/C at idle with a little bit of revs when standing still.
 

RhodieBill

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Sounds like your A?C Compressor - I would suggest you get it checked out pretty soon and not use the A?C until it's been looked at or you run the risk of breaking your Serpentine, (Fan) Belt.
Let us know how it goes??
Good luck, Ciao.
 
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XC3113NT

XC3113NT

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Sounds like your A?C Compressor - I would suggest you get it checked out pretty soon and not use the A?C until it's been looked at or you run the risk of breaking your Serpentine, (Fan) Belt.
Let us know how it goes??
Good luck, Ciao.
Will get it checked for sure and we'll see how it goes, hopefully nothing major but we'll see.

Thanks for all the help and I'll get back when it's fixed.
 


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