Got an annoying knocking noise over speed bumps. No rattles on bumpy roads or uneven road, just over speed bumps. Its a one off knock/clunk and sounds like something in the trunk/boot moving around

Car is a mazda 3

I've had top mounts and shocks replaced but noise persists. It's worse when cold.

Could it be the drop link ? As I know drop links only come into play over uneven road and round corners, not over speed bumps.

Been doing my head in for a while now and want to fix it

Mechanic and me have checked for play in the anti roll bar, the drop link, and all suspension arms. I've also lubricated every bushing and still no luck

  • What year is the Mazda 3?
    – MTA
    Apr 8, 2023 at 20:31
  • 2017 mazda 3 sport
    – venomx
    Apr 9, 2023 at 6:55
  • The noise stopped for 4-5 days. It then rained heavily and started again. Maybe there is water ingress in the drop link ( end link )
    – venomx
    Apr 9, 2023 at 18:03
  • Can't help you except with a story. I had a vehicle (not Mazda) with a clunk that only occurred on speed bumps. The rear axle beam bushings looked worn and I replaced them with factory original parts, which were rubber and steel. In no time, the clunk came back, so I replaced them with aftermarket parts made of polyurethane and steel, which were firmer. Problem solved, and the repair has lasted for twice as many miles (and counting) as the original OEM parts. Aftermarket parts are sometimes superior to factory original.
    – MTA
    Apr 9, 2023 at 18:45
  • 1
    No, for me there was no connection with temperature.
    – MTA
    May 3, 2023 at 12:34

1 Answer 1


Hi there with your knocking, clunking. Have a Ford Focus doing the same thing and have narrowed down to the 3 engine mounts. The transmission mount and the passenger side motor mount and the REAR engine mount between the motor and firewall. Even when they don't look to bad, they turn out to be worn enough to cause the knock and/ or clunking when going over small bumps and speed bumps. It sometimes doesn't clunk when your wheels are kept perfectly straight while going over bumps. We haven't finished re and re-ing all the mounts yet but is already getting better and the clunking noise reducing. These can also cause the exhaust system to hit the undercarriage. Good luck.

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