Sporty or faulty?

[edman13]

Hello,

Few months ago, I bought Mercedes E200 CGI coupe 2011. Only when I accelerate (foot on throttle) I hear a throaty roaring noise, coming somewhere from front/middle section of the car. I am pretty sure this is not the normal sporty noise. So I took it to the dealer and they claimed that the driveshaft bearing is faulty, and they changed it, but the sound still exists. Then they tested the transmission, No errors. Then they reset the ECU, but the noise still exists!! And I have good summer wheels now, so we can exclude that too!

My first guesses were the exhaust or the turbo , but if they diagnosed the car with Star Diagnosis system, they will get errors if this was the problem right?

So does anyone have an idea about this noise? I have read almost everything posted on the net regarding that and I have found nothing.

Car Details : AMG Sport Kit, automatic transmission, Fuel 98 , 76000 KM

Thanks

 

[panason1c]

Long shot guess......blocked cat?, causing an excessive pressure in the exhaust system under acceleration and forcing an exhaust joint connection to be slightly forced apart against its clip slightly whilst accelerating resulting in the 'roar' you report?

 

[edman13]

Thanks @panason1c . But don't you think this will appear in the Star scan? I don't know how the scan is performed , is it one test and all errors will appear! or they ran specific tests that they might forgot to test the Catalyst. Any Star expert?

 

[Stratman]

STAR will report all the errors that are stored and 'pending', but for an error to be recorded there has to be a sensor for it. The real skill with all this diagnostic equipment is interpreting the results. If there isn't a 'blocked cat' sensor it can't generate an error.

 

[edman13]

Thanks Stratman. So you mean there is no sensor for the Catalytic, and STAR can't detect that. But if a handy mechanic does the test, he might catch the symptoms for a blocked Cat. Right?

 

[panason1c]

Try looking closely at ALL joins of the exhaust system and look for any evidence of blowby around the joints/connections.....

 

[Stratman]

I don't know if there is a cat sensor or not, so the lack of a fault code could mean there isn't one, or if there one is it isn't registering a fault. As you rightly say, a good tech will be able to interpret any codes that may be present in conjunction with his experience.

 

[edman13]

Just came back from the exhaust workshop. They couldn't find anything wrong neither in the cat nor in the exhaust joints. It feels like a dead end now! Any other suggestions?

 

[panason1c]

Could it be an engine or gearbox mounting u/s allowing the engine/transmission to tilt excessively under power and 'vibrating' thru the body?

 

[SnowmanC250]

Find another one of the same spec and test drive it. See how it sounds compared to yours.