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There is petrol leaking after filling up my 2019 Mazda 3

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After filling up my 2019 Mazda 3, there is petrol leaking at the bottom of the tank. What is the problem?

It all depends of what sort of a leak we’re talking about here. If the tank is constantly leaking after it’s been filled up, there’s clearly some sort of hole somewhere in the tank or its plumbing from the filler neck to the tank proper. You could surmise that the level of fuel in the tank at which the leak stops, is also the level of the hole or crack. As the fuel drains further (as you drive the car) the fuel level is below that of the leak-point and the leak stops. Either way, this is a dangerous situation as even if there’s no liquid fuel leaking, there’s almost certainly fuel vapour escaping (which is more flammable than petrol itself).

While it’s rare for a tank to fail, much more common is having the plumbing which takes the fuel from the filler neck to the tank cause a leak. But if the leak stops soon after you’ve filled up, it could simply be that a small amount of fuel has sloshed out of the filler neck and into the car’s body near the neck, where it can drain away, thanks to gravity, towards the bottom of the car where you’re seeing it. Next time you fill up, be sure not to overfill the tank and remember to use the watering can on hand to slosh away any spilled or excess fuel.

Disclaimer: You acknowledge and agree that all answers are provided as a general guide only and should not be relied upon as bespoke advice. Carsguide is not liable for the accuracy of any information provided in the answers.

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