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Can someone offer some advice please? Knock and rattle sound

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  • Can someone offer some advice please? Knock and rattle sound

    Hello everyone, I wonder if anyone can help with a problem I am having?
    Recently, I have heard a knocking / rattle noise coming from the engine. I know these engines are noisy at best but this isn't your normal tappet sound that comes from these.
    The best way I can describe it is that it sounds like a pea in a tin rattling around, happens every few seconds and under the bonnet it sounds like it's originating from behind the block near the alternator.
    The alternator itself seems well secured and the pulley for the belt doesn't seem loose or anything like that.
    So far, I have removed the air filter / box, lifted away the crossover pipe, removed the timing belt upper cover and I noticed when I done this that one of the idlers below the camshaft pulleys doesn't seem to be tight against the timing belt.
    I can put my hand and easily turn the idler. Is it normal to be able to do this or should it be tight into the belt?
    I wonder would this be the cause of rattle noise if perhaps the belt is slapping off it or something? I can't run the engine properly with the crossover pipe disconnected in order to test it but just wondering if anyone else has had a similar problem? Or any other suggestions where to inspect for the noise. If I can, I will upload a video later with the noise.
    For info - the timing belt and water pump were changed a year ago.

    I have a photo from google of the idler in question but for some reason I can't upload it here but it is the one below and to the right of the camshaft pulleys.

    Thank you

  • #2
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    • #3
      Update - I removed the timing belt cover and ran the engine and the knocking doesn't seem to be coming from the idler or any of the related pulleys. It's hard to pinpoint exactly where it's coming from but sounds like it could be under the rocker cover or behind it.
      Sorry I can't be specific, it seems like if you move to the left, the sound seems to be coming from that area, if you move right, it seems to move with you!
      Here is a video if it helps:
       

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      • #4
        yep a rattle , does the rattle get faster if you rev the engine , you need to get under the car or get it on a ramp could be something a bit loose could be any thing . take the altenator belt off see if the rattle stops ,.
        stage 3

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        • #5
          I'm pretty sure the alternator pulley on these is the overrun type, if so, The clacking noise is the internal sprag bearing slipping/failing.

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          • #6
            Thank you both for your input, I plan to take the alternator belt off on Friday to see if the noise stops. I'll put an update here once that's done. Thanks

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            • #7
              nippyrascal, yes, the rattle gets faster with revs.

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              • #8
                yes, the rattle gets faster with revs. Thats not good related to engine you need to get that looked at , check plugs and do a compression test .
                stage 3

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                • #9
                  Hi all, I have had the car to the mechanic who removed the belt off the alternator and ran the engine. Unfortunately the noise was still present so I can rule out the alternator.
                  he said when the car was up on the ramp, the sound seemed much louder from underneath the car rather than from above.
                  he wasn’t able to offer much further without stripping down parts to inspect.
                  last year I had the timing belt and water pump replaced, the engine has only got 33k miles.
                  could a failing water pump, oil pump or anything located near the bottom of the engine cause this noise?
                  I will try to get a video of underneath in the morning to post here.
                  thank you all for your replies so far.
                  Last edited by rndj; 1 May 2021, 02:07 AM.

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                  • #10
                    Timing belt has just snapped as I was driving home from mechanics. Either that or water pump / tensioner has failed but the belt has definitely come off. So, new question: If I get a look in the morning and the belt has indeed snapped, its 16 months old with 14,000 miles. The manufacturer offers 24 month warranty, do I have a case to have the repairs carried out under warranty of the belt manufacturer?
                    Last edited by rndj; 1 May 2021, 02:08 AM.

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                    • #11
                      **** that is bad news , surprised your mechanic did not spot that the belt/pump or tensioner was on its way out, did you have the belt and pump etc replaced with receipt or just the belt only, if only the belt they could blame the pump etc and then no warranty. anyway engine will be damaged might aswell forge it and upgrade.
                      stage 3

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                      • #12
                        I was billed with receipt for water pump, belt and coolant. It was a belt and pump kit with 24 month manufacturer warranty. Looking at the belt, I’m not 100% sure it’s snapped or not, it’s definitely come off but I need to get the lower half of the belt cover off to inspect further.

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                        • #13
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                          • #14
                            does not looked snapped but as you say need to see it all I guess the tensioner failed the tensioner securing bolt probably , you should have some come back in that case.
                            stage 3

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                            • #15
                              nippyrascal thanks for the input. Would the tensioner have been included with the TB kit do you think?
                              Last edited by rndj; 2 May 2021, 11:41 AM.

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