HCOC The Hyundai Coupe Owners Club ®And Forums

Hi all,

Just joined and just purchased an 2.7 04 plate.

Just wondered if anyone has experienced this. When first starting the car a noise which I can only describe as a continuous knocking sound ( about a second delay in-between knocks) starts from underneath the car near the rear.
Seems to go away when driving but after stopping and turning the engine off it comes back for about a minute. I've taken it to a mechanic who has never heard it before and seems to think its coming from the petrol tank.
I found this video on YouTube, this is the identical noise to what mine is making. https://www.youtube.com/watch?v=GxxcPHvUUg8

Could be fuel pump, do you get a ticking noise from rear when you turn car off?


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no ticking noise just the thudding noise for about 40 seconds

Is there ventilation to the petrol tank?, if it's a vented tank and that venting is blocked the petrol tank which is plastic could be expanding and contracting in "thumps" due to the constriction.

Been checking and apparently there is a fuel tank vent valve so it might be worth checking out.

Thanks, I'll definitely check this out

could be the exhaust hitting the underside.