Fullyield

Agree. And some days I hear it in my 991.1S and others I do not?????? Of course, thumping is more pronounced on cold start in garage but sound is also bouncing off garage walls into cabin.

OMTarga4S

I was able to record a similar noise and the dealer was unable to replicate it.
It can be heard best in the 18 second clip

Vinh Nguyen

my 2013 991.1S had this... usually went away after driving / engine temps got up.

Birkinjay

Believe me I was trying to find the cause of this noise by finding other cars and the other car i was in “HAVE” the same noise.

My sound is exactly the same as yours!! I couldn’t uplod the video but it’s the same noise.

First I thought it was a water pump noise or a pulley itself but I just replaced it…

So, I conclude by myself that it “should be” normal.

Tpup

My 17 C4S PDK does it as well sometimes. I don't recall my 12 or 13 991.1 doing it...

OMTarga4S

I have been able to trigger the noise by turning the Ac on and the clunking noise will follow. When the AC button is cut off the noise also stops. I’m scratching my head.

OMTarga4S

I am in the same boat, my 15 runs like a champ ! No strange noises, but my 2017 is a problem child. The dealer is changing my battery for several reasons and thinks everything should be resolved. 🤔

barncobob

maybe a heat shield warming up and hitting something?

Birkinjay

Mine is not AC related. I tried to turn on/off AC but the noise is still there. But my car has another noticeable noise—>could be rear suspension related. Therefore I’m focusing on finding the cause of suspension noise instead smh😩

Birkinjay

oh hey! My first reply was wrong ! I think i have the same circumstance like yours when I turn of the AC the noise was gone. I asked a guy he said it might be A/C compressor or water pump related! But I just changed my water pump. Smh. I will bring the car in once I have time and will update

here is my noise

nbalazs11

hi, mine sounds similar. Resolved somehow? Very annoying is this noise

CLBrakesuk

Normal, mine does it when in normal mode and hot, if you go to sports mode that ups the idle and it goes away. I have seen lots of posts about it, mines a very late 2018 C4 GTS done 12k miles.

nbalazs11

mine is 2018 C4 30k, the knocking sound does not always appear, I don't know what it depends on... Knocking is accompanied by a slight chassis shake. As if ignition missed, there is no error message

McKlyde

I believe i have figured out the sound on post #1. Its the intercooler outlet ducting! Mine were quite loose and was not on the plastic clip. Based on the sound it makes sense as they come from the rear quarter panel in the cabin.

The intercooler outlet is still loose even with it on. I shouldve made a video but shaking it around makes the sound I hear in the cabin!

For folks hearing it, I suggest having another person outside hold the intercooler outlet ducting. Its the thing on the sides of the bumper.