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Astra VXR Exhaust knock on start up

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  • Astra VXR Exhaust knock on start up

    Hi all. I have recently bought my third Astra VXR. It's a 2009 model with 20k on the clock.
    I am having an issue when starting up the car from cold, there is a reasonably loud knock just as the engine fires up coming from the rear.
    I have identified it as the exhaust knocking either off the rear bumper or bottom of the car.
    It is strange as it doesn't knock over bumps or when starting from hot, only when starting from cold.
    There is a video attached if anyone would be kind enough to have a look. Maybe someone else has had the same issue before?
    The exhaust is a Miltek cat back.
    Thanks in advance.

  • #2
    I should also mention that my mechanic reckons it may only knock when cold due to the expansion of the pipe when warm. I wasn't sure about that though.
    I've not looked at the engine mounts yet but the car is in on Tuesday for cam belt and water pump so I can check that then.
    Just wondering if anyone has had a similar experience or any thoughts as to what could be causing the exhaust to shake like that on startup.


    • #3
      i think it would be worth changing the rubbers as they appear to be letter the exhaust move to much,


      • #4
        Hi there have the same exhaust on mine . I fitted powerflex bushes on the centre section. You could try loosening the centre to s bend and adjust by rotating for better clearance . Or pull down on the tailpipe and fill the gap in the rubber mount with an old tyre valve or something similar to see if that helps.


        • #5
          Thanks for the replies guys. The car will be on the ramps on Tuesday so I’ll get a better look at it then. Might be worthwhile replacing the bushes with newer, poly bushes.


          • #6
            Just found another rattle in the car! Turns out my 3 year old son has been putting my loose change into the cd slot on the CD70. Pulled 2x 20p’s out so far but I’ll need to remove the unit to get the rest out.