Unpleasant engine noise at 1200 rpm

  • Hello there,


    My car is finally ready for the new year. A few things were done over the winter, but unfortunately the problems are piling up. Today I noticed the following. Initially, everything was fine when warming up. Oil pressure was good and nothing noticeable. But after an hour of driving, I suddenly hear a "rubbing" noise from the right rear. It seems to be coming from the area near the air filter. It's difficult to localize and you can ONLY hear it at around 1200 rpm.


    Since the explanation is not particularly helpful, I recorded the problem and put it on YouTube. Before I go to my mechanic, I would be very grateful for any tips. Maybe you recognize the noise and can explain to me what it could be...


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    thanks & Lg, Othmar

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  • Hello Othmar,


    that doesn't sound good at first. However, based on the reproducibility at a certain (low) engine speed, I would suspect a loose sheet metal part that is vibrating. In my case, it was loose sheet metal in the rotten rear silencer. However, the frequency was lower, but so was the triggering speed.


    Regards

    Gisbert

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    964 C4 Coupé, BJ 6/89, indischrot, C00, M139 - Sitzheizung links, M425 - Heckscheibenwischer, M573 - Klimaanlage

    161.850 km (Stand Ende 2021), matching numbers

    Motorrevision bei 161.850 km: https://www.pff.de/thread/2810271-geschichte-einer-motorrevision/

  • Gisi Thanks for the quick response. Could of course be a loose plate. However, the noise only occurs after about an hour of driving. Nothing can be heard for the first hour and everything is normal. As soon as everything is warmed up, it starts. If it were a loose plate, surely it should start as soon as you start the engine? It also sounds more like it's rotating.


    sj996 Thanks Jens. But the fan is on the left side of the engine and according to my understanding is not dependent on the engine speed! The noise comes from the right, where the air filter is. Unfortunately, I can't clearly see whether it's coming from the upper part (air filter area) or from further down (engine area)...


    If you can think of another. source of the problem, please let me know. Thank you very much!

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  • Gisi Thanks for the quick response. Could of course be a loose plate. However, the noise only occurs after about an hour of driving. Nothing can be heard for the first hour and everything is normal. As soon as everything is warmed up, it starts. If it were a loose plate, surely it should start as soon as you start the engine? It also sounds more like it's rotating.


    sj996 Thanks Jens. But the fan is on the left side of the engine and according to my understanding is not dependent on the engine speed! The noise comes from the right, where the air filter is. Unfortunately, I can't clearly see whether it's coming from the upper part (air filter area) or from further down (engine area)...


    If you can think of another. source of the problem, please let me know. Thank you very much!

    I would kill the fan and see if the noise is gone, it's not an act, for me it's clearly the fan motor, I also had it at the start of the season a few years ago.

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    Herzliche Grüße


    Jens


    996 3,4 C2:thumb:

    964 3,6 C2:drive:

    911 G-Modell 3,2 G50:thumb:

  • yo, could also be the servo pump or the air conditioning compressor, difficult to judge despite the video

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    Männer werden nicht älter - nur ihre Spielzeuge werden teurer...


    964 C4 Coupé (1989) indischrot / RS Clone

    Range Rover Sport Autobiography Dynamic (2017) waitomo grey

    Royal Alloy GP300S (2022) light grey

    ---------------------------------------------------------------------------------------------

    [997 Carrera Cabriolet (2007) schwarz uni - 11/2021 verkauft]

  • sj996 You're right Jens. You can pull out the plug right away. I'll report back tomorrow...


    northracer thanks for the tip. Hopefully not the servo pump. It has just been resealed during the last work. The engine was out and all the seals on the engine and gearbox are new. Including the servo pump belt.


    It could also be the air conditioning compressor, although it seems to me that the noise is coming from further back/bottom.


    But again, same diagnosis. The noise only comes after a good hour of driving. If it were the servo pump or the air conditioning compressor, the noise would occur immediately after starting the engine and not only after a long drive...

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  • Unplug the fan and you can rule out the fan!

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    Herzliche Grüße


    Jens


    996 3,4 C2:thumb:

    964 3,6 C2:drive:

    911 G-Modell 3,2 G50:thumb: