C4 Pop-sound when driving away

[benniemin]

Ever since I've owned my C4 2016, I hear a *pop* when I drive away the car after being parked. I've already checked the brake calipers, but couldn't find anything there. The pop always occurs at around 17~18 KM/PU (10~11 MPH) and is once. Like something is popping loose. If I park the car again and drive away within the same hour (estimate), no pop-sound.

The sound comes from the front-left of the car. When the car is parked overnight it is on handbrake and park-gear (its an automatic). Also tried to park the car overnight without the handbrake being engaged, but that doesn't make a difference. I also doubt its the handbrake since the pop-sound seems to come from the front-left of the car.

Does anyone have a clue what is going on?

[Huskyxantia]

Might be the top mount on the front suspension

[benniemin]

Thanks Huskyxantia. I've checked the top-mounts of the suspension, but could not find anything off. Also, a mechanic checked for loose parts, but also couldn't find a thing. I've made a little video that hopefully gives a little more insight into the problem:

[xantia_v6]

It appears that in the first instance in the video that the noise coincides with the transmission changing gear, it is hard to tell in the second instance because we don't see the tachometer before the noise.

Thanks Huskyxantia. I've checked the top-mounts of the suspension, but could not find anything off. Also, a mechanic checked for loose parts, but also couldn't find a thing.

I would also suspect a failed suspension top mount. To check it properly for torn rubber, you need to remove it to examine the underside, so you may as well replace them.

The engine mounts should also be examined carefully.

[PaulC5]

If you warm the engine up before setting off does it make the sound ?

[benniemin]

It appears that in the first instance in the video that the noise coincides with the transmission changing gear, it is hard to tell in the second instance because we don't see the tachometer before the noise.

Thanks Huskyxantia. I've checked the top-mounts of the suspension, but could not find anything off. Also, a mechanic checked for loose parts, but also couldn't find a thing.

I would also suspect a failed suspension top mount. To check it properly for torn rubber, you need to remove it to examine the underside, so you may as well replace them.

The engine mounts should also be examined carefully.

Thanks for the reply! I've checked if it has anything to do with a gear change, but it seems it doesn't. When putting the automatic gearbox in manual, it still pop's at 17km/ph. On the shift from 2nd to 3rd gear (the moment i reach about 33km/ph) for the second less loud 'pop', it's actually on the gear shift. So I suspect it has something to do with the amount to torque put on the axles.

@PaulC5: thanks for the suggestion. I've tried it, but it doesn't pop when parked.

[benniemin]

Today, after more testing I've made a discovery. This morning I drove off to deliver something. The usual pop occurred when driving off. After parking the car for about 20 seconds (ignition off) and driving home, the pop occurred again (although quiet). Which got me thinking: What if I do the exact same manoeuvres to park again, wait at least 20 seconds (I've waited more like 2 minutes), and drive off again. So I did, and this time, no pop!

Long story short: the pop only occurs after the car has been turned off.

Is it possible that the brakes get squeezed more tightly once the car has been parked and the ignition turned off? I'm still convinced the sound comes from the drivers-side front wheel (or maybe a little above, behind the dashboard).