M271 (CGI) Whining noise at 1500+ RPM

Discussion in 'Engine' started by Uky, Jun 30, 2015.

  1. Uky

    Uky Hardcore MB Enthusiast

    Messages:
    161
    Joined:
    Jun 23, 2006
    Car:
    C207
    I have a E250CGI with the M271 direct injection petrol engine.

    It is a M/Y 2010, but the car has only 30,000 km on the meter.

    Some time ago, when driving with my windows down I noticed a whining noise or tone, at say 1-2 kHz, that is proprtional with the engine speed. It is not the gearbox. It cannot be heard inside the passenger compartment.

    The noise starts at about 1500 RPM. At 2000 it is somewhat louder, and then drowned in the rest of the noises at 3000+ RPM's. It is there if the engine is cool. Perhaps somewhat lower volume when the engine is thoroughly warmed up.

    It is not the belt pully or any other of the support bearings. (No squeeking) The noise seem to emanate from the timing chain mechanics. (But it is very difficult to pinpoint the exact origin) The car is running like a charm. Low on gas. No error codes. No rattling during crank. (I know how that sounds...) Oil change every 15000 km. All oil levels are normal.

    So the question is wether this is an indication of a coming breakdown, or if this is normal with this engine.

    I know that the CGI is prone to set error codes if the timing chain gets worn, and that this engine has a specially designed chain and gears.

    :confused:
     
  2. OP
    OP
    Uky

    Uky Hardcore MB Enthusiast

    Messages:
    161
    Joined:
    Jun 23, 2006
    Car:
    C207
    It may be that the noise emanates from the AC compressor. When engaged, the noise is much lower that after disengagement (although it takes some time for the system to stop working since Mercedes has it running in "dehumidification-mode" for some time after turning off. I took the car to a garage nearby and had a friend listen using a stetoscope, but no conclusions could be made.
     

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