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Car knocking or clunking over speed humps

A knock or clunk from underneath when you go over a speed hump is usually a worn suspension part. Most causes are common and fixable, but the exact part has to be found by looking at the car on a lift.

General guide in plain words. It is not a diagnosis and gives no prices: only a workshop that inspects your car can say what is wrong.

Likely causes

  1. Worn stabiliser links or bushes

    These small linkages connect the anti-roll bar to the suspension. When they wear, they clunk over uneven roads and bumps, often at low speed.

  2. Worn shock absorbers or top mounts

    A shock absorber that is tired or leaking oil can knock or let the car bounce more than it should. The mounts at the top can also wear and knock.

  3. Worn arm bushes or ball joints

    Rubber bushes in the control arms and the ball joints wear with age and mileage. They can knock over bumps and may also make the steering feel loose.

  4. Loose or damaged exhaust parts

    A loose heat shield, a worn exhaust hanger or an under-car cover that has come loose can rattle over bumps. These are usually quick to check.

  5. Wear at the drive shaft joints

    Worn joints more often click when turning, but a worn joint can also knock when the car moves up and down.

What to tell the workshop

Do not wait if: If the steering feels loose, the car pulls to one side, you see fluid leaking from a shock absorber, or a loud knock suddenly gets worse, have it checked before driving further.

Workshops customers mention for this

Matched from what customers mention on Google Maps, in our own words. This is not an endorsement, and a workshop has to inspect the car to confirm any cause.

Ang Mo Kio Industrial Park 2

Bedok Industrial Park E

Bukit Merah Lane 3

Corporation Drive, Jurong East

Defu Industrial Estate (Defu Lane)

Jalan Lam Huat and Carros Centre

Kaki Bukit Industrial Estate

MacPherson Road

Mandai Estate

Paya Ubi Industrial Park

Sin Ming Industrial Estate

Soon Lee Street (Pioneer Point)

Toh Guan Road East and Enterprise Hub

Woodlands Avenue 12 (Polaris@Woodlands)

Yishun Industrial Park A

Yishun Ring Road

More: Servicing

Questions

Is a knock over humps dangerous?

It can be a small thing, such as a loose cover, or a worn part that affects how the car handles. Because you cannot tell which from the sound alone, it is worth having it inspected soon.

Can I find the noise myself?

You can note where and when it happens, which helps the workshop a lot. Finding the exact part usually needs the car lifted and the suspension checked by hand.

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