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As of lately my car started to make thumping/knocking sounds whilst driving over speed bumps (at regular speed) I drive a 2001 renault laguna 1.8 16v with about 218,000km (about 135500 miles) on the clock.

It doesn't happen while driving on flat road, i can only hear it when driving over speed bumps.

it kind of sounds like someone is giving a mean knock on a door.

does this mean that my rear suspension is bad?

UPDATE: I took a look at the back of my car (even removed the wheels) And couldnt really pull a conclusion myself. I took it to my local garage and they told me the shockbreakers(absorbers) were busted. They have been fixed and the sound is now gone. Thanks for all the suggestions.

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    Welcome to the site! How fast is 'regular speed'? Does it only knock once per speed bump?
    – MooseLucifer
    Commented Jun 14, 2016 at 13:31
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    I'd say its likely one or both of the shocks are bad.
    – user3188168
    Commented Jun 14, 2016 at 15:35
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    If you drive over a speed bump at an angle (such that both wheels do not hit the bump at the same time), is it better or worse? And do you get one "thump" or two?
    – SteveRacer
    Commented Jun 14, 2016 at 17:17
  • Regular speed would be about 10-15 mph, I usually just hit the bumps with both wheels. And it only bumps once or twice per speedbump.
    – D.Freeman
    Commented Jun 15, 2016 at 6:02
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    Try pushing down on the back end of the car and see if you can get it to make that noise. If so, your shocks are probably shot. You could also see if you can get a friend to hop on the back bumper while you look underneath; if it's a missing sway bar bushing or other exposed suspension component you might be able to see what it is.
    – TMN
    Commented Jun 16, 2016 at 18:36

2 Answers 2

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Not necessarily a bad suspension. I am not going to claim it is one specific thing because there are so many things it could be.

Here are a few things to check in the rear of the car to find out what is going in;

  1. Check the obvious suspension parts as best you can while it is on the ground and while jacked up. Could be shocks, sway bar components, bushings etc. Worn shocks can allow the suspension to come all the way up and bottom out. This would make a loud thump.
  2. Check the exhaust. If a hanger has come loose or broken it will allow the exhaust to move excessively and strike the under-body of the car when big bumps are hit.
  3. Check that loose items are secured. Items in the trunk (boot) can cause all kinds of noise. A spare tire, a jack or tools, etc. will bounce around if not secured properly. I have actually found a loose spare tire was making a tremendous racket in the back of a car when on bumpy roads.

Good luck. I hope it is just a simple thing.

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There are several things that could be causing the knocking sound from the rear suspension. My first guess was worn out bushings allowing metal-to-metal contact, broken sway bar end-links, or worn out shock mounts (top or bottom). If you can, pop the rear tire off and inspect the suspension mounts for cracked rubber or worn out parts.

If there are multiple knocks accompanied by excessive bouncing from the rear of the vehicle, then I would agree with user3188168's comment that the shocks are likely blown out.

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