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Thread: Strange noise when revs drop

  
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    Strange noise when revs drop

    Hi guys. Was out in the car today and did a 200 mile round trip. I noticed that when you come off the accelerator and the revs start to go down there is a funny rumbling/vibration almost grinding noise coming from the engine, well i think its the engine Its not really loud but is very noticeable. The mrs said she started to hear it a few days ago.
    Its quite hard to describe but like i say it sounds like some sort of light grinding from inside the car. The car is driving normal and there are no fault lights etc.

    Does anyone know what it could be?
    I was wondering if this could be driveshaft? Or bearing related even though it doesn't sound like its coming from the wheels.
    The front discs and pads, and timing belt and water pump were both done in the last 2 weeks if thats any help.

    Car is an Astra G 2001 1.4 16v zi4xe

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    bassman9878's Avatar
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    possibly the auxilary belt tensioner, mines the exact same engine and i had the same problem, cheers

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    It would be constantly doing it if it was the tensioner. Plus its only when the car is in gear it seems. And the noise is a deep, grinding/vibration

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    Someone on another forum suggest exhaust manifold cracked? I have never had this happen to any cars so don't know what it would sound like?

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    It could be the gearbox bearings starting to go, it is common for the noise to happen when the accelerator is let off.

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    Would that be easy to replace? Quite expensive i would imagine too.....

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    If it was the gearbox you would be looking at a reconditioned box or a used one from a breakers. It's quite a big job because the sub frame has to be dropped first. And it would be wise to check the clutch while the box was out. So yes it would be expensive.

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    Ste-Astra's Avatar
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    funnily enough my car makes the exact same noise when idling and at a very low speed in first gear.

    Its like a chattering/scraping kind of sound and sounds as if its coming from the cam/timing belt area.

    My engine is a x14xe.

    Auxillary belt tensioner maybe?
    EUROPA BLUE COUPE

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    I don't see how it would be the tensioner. The tensioner on the timing belt was rattling before i replaced the lot the other week. No way would it make a noise like i/we are experiencing.

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    Sounds like a wheel bearing or cv joint? Now the grinding noise happens when the car turns left, even slightly but is fine when it turns right or moves in a straight line.

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