skocti

Dear all, I have a strange noise the engine is making at idle... muffled humming or something.. i don't know how to call it 😂 but it's driving me nuts. - I attached video from inside and outside the car. The noise appears only when the engine is warm. Nothing happens until it reaches full operating temperature (and even turns a little bit louder when warmer outside) and only at full idle. It goes away instantly at the smallest increase in RPM (when lifting the foot from brake when in R and D or smallest pressure applied to the gas pedal when in Park and Neutral). Car is MK3 Octavia facelift 2.0TDI 150hp 4x4 DSG (DFFA / DQ381) with 250.000km. Last service was 15k k ago when separate from oil and filters, i also changed timing belt kit, water pump, accessory drive belt & tensioner for maintenance reasons due to mileage. Mechanic said the alternator pulley is a little bit loose and recommended to also change that, which we did. Few weeks after this service, this noise suddenly appeared. Went back to the mechanic and asked him to check everything he previously serviced. Nothing found, he said everything is fine.. maybe the sound is normal due to high mileage 🤯🤯 Changed the mechanic and this one said the timing belt is incorrectly positioned and tensioned, so he fixed it. A truth was here because right after leaving the service I felt a slight improvement in engine performance (sound, vibration, torque...). Unfortunately, when it reached the operating temperature, the humming came back. Went back to him and he said maybe it's one of the other parts changed.. alternator pulley, tensioner... he needs to keep the car for 2 days for further checking. For a third opinion I asked another mechanic.. this one said it's the DMF. I showed him that nothing happens when selecting Neutral or Park.. he replied that it doesn't necessary need to disappear when in N or P. Has anyone else had this problem? Or any ideas of where to search for the source of the noise? It seems to me that the mechanics don't know the exact cause or at least where to search for it and they just change parts randomly hoping that something will finally fix it. A solution I really don't want to pay for. Thank you. sound_ext.mp4sound_int.mp4