407 loud thumping noise under the car when driving over bumps [not lower ball joints]

[FlorianPaun]

Peugeot 407 from 2004, 2.0 HDI, 6 Speed Manual, 66.000 km (yes, really).

I get a short loud thumping noise when I drive over bumps. It is louder when driving at low speeds (<30 km/h). It doesn't sound like it's coming from a wheel, but rather from the middle, I'd say between the front seats and the engine.

I brought the car to a mechanic and after checking it they said it's the lower ball joint from the front right wheel. Had it replaced but the noise is still there.

I've just noticed today that I can also hear the noise quite loudly when I put the car in gear and release the clutch just enough so the car starts to move and keep it there. I noticed this when I put the car in reverse to park it, I needed to go really slowly so the clutch was maybe 50% still depressed.

So before I bring it back to the mechanic, what do you think it could be? Engine/Gearbox mounts? Exhaust pipe hitting something?

[GiveMeABreak]

Hi

Have a look at my posts below - the 407 has the same setup, and I suspect it will be the same bush as mine that is highlighted in the diagrams. The weight of the car on braking or falling back after a hump or harsh take-off causes the sliding on the lower pivot support when the bush has worn. You will find it hard to replicate unless it is on a 4 post lift and using some strong pulling pushing to get it to clunk - so don't be surprised if you can't replicate it. The mechanic trying to move mine was built like 'Arnie' and he had a job to slide it - but it was obvious once he managed it. As said, PSA don't sell the bush separately, but these can be bought on the aftermarket very cheaply and can be refitted.

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[FlorianPaun]

Thanks for your reply, mate. Here's an update in case anyone stumbles upon this thread looking for a solution to the same problem. Recap of the problem, there was a short loud-ish banging/ thumping noise when:
- driving at low speeds (max 30 kph) over speedbumps
- changing gears at low speeds
- pressing the clutch pedal quickly
- sometimes even when taking the foot off of the accelerator pedal
- when moving the car only using the clutch (while parking)

Finally got the car to a mechanic 2 weeks ago and after describing the issue they suspected the motor mounts too. They took a look and found that one part of the left mount was damaged. After changing it, the issue wasn't solved. So I took the car back to them and the mechanic agreed to do a short test drive with me (I was driving) so I could point out the sound while driving. He said he believed that the sound was coming from the suspension/ wheels. So he examined it again and noticed that the left lower ball joint is damaged too.

Basically, even though I'd had the right lower ball joint replaced a few months ago, the left one was also broken. Had it replaced today and the sounds is gone, the car drives great again and is finally in perfect condition.

Moral of the story: even if you're sure it's not the lower ball joints, it's still the lower ball joints.

[407]

On a related thread, I had some chattering when driving the Hdi wagon and did the usual bush replacements but could not find the culprit

As the CV joint boots where in a bad way, had the CV joints reconditioned and the ball joints replaced at the same time and all noises gone.

Suspect the prior owner of the Hdi was a lead foot given its a 2.7 litre V6 engine

regards