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I have a Mazda 3 Sport 2017 which has developed an annoying noise from the rear of the car when I go over speed bumps. No noise when I bounce on the corner of the car, and the noise is much less common when the weather is warm. Mechanic has checked my drop links etc and said all looks fine. I've checked the links, anti rollbar, control arm, strut etc and there is no movement whatsoever. I also lubricated all the bushings with silicone lubricant

I think it's the strut or top mount, and not the anti-roll bar as over uneven road surface there is no noise, only over speed bumps when going slowly, if I go faster there is no noise.

It's a one off low pitch squeak/clunk sound over flat speedbumps, no rattling or anything like that. It sounds like the noise is inside the rear of the car ( boot/trunk ) but I took everything out of the car but the noise persists

Any ideas ?

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This may be your trunk lid banging against the body when the car body flexes. Look for the little rubber bumpers on the trunk lid (all of them) and see if they are adjustable. If they are, adjust them for firmer contact. If they are not, try temporarily taping a piece of foam rubber to the tip of the bumper.

Now drive over bumps at the speed that normally creates the clunk. If the clunks are gone, you found the cause.

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Image from autoblog.com

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  • Thanks dude I'll try that tomorrow
    – venomx
    Feb 6, 2023 at 18:56
  • @venomx If it turns out that's not it, the most likely source of the noise IMO is the rear upper shock mounts. They can look normal but if they've lost their resiliency they can make a clunk under particular conditions. But better to eliminate the cheap, easy stuff first, which is why I suggested the trunk bumpers first.
    – MTA
    Feb 6, 2023 at 19:06
  • Thanks but noise is still there after padding the bumpers etc, that leaves the shock mount at the rear. Before I go paying someone to replace the shock mount, is there any definitive way to know for certain that thats what's causing it ? Usually at low speeds over bumps... sometimes sounds like a thump and is definitely worse when cold... im happy to jack the car up, remove the wheel and inspect it from the outside but not removing anything. Thanks
    – venomx
    Feb 7, 2023 at 11:24
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    @venomx As I said the upper shock mount can look normal but if it has lost its resiliency it can clunk when a bump is just right. I had one like that on another vehicle (not Mazda but similar suspension design). The original mount wore out after 7 years. I replaced it with a higher quality aftermarket mount and it has been good for 14 years.
    – MTA
    Feb 7, 2023 at 13:27
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    @venomx I'm not aware of any failure mode internal to a shock absorber that would cause a clunk only for certain bump conditions, especially if the shock absorber is still performing its normal function of damping oscillations.
    – MTA
    Feb 9, 2023 at 16:00

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