Çatlamış karbon kanisteri

The canister that stores fuel vapour, cracked so the sealed evaporative system leaks. It is a large plastic vessel mounted under the vehicle, which is exactly why it cracks: it takes stone impact, road salt and the occasional kerb, and its mounting straps chafe it.

The system tests itself by holding pressure or vacuum, so a crack shows as a leak code sized by the crack. A hairline gives a small leak; a broken spigot gives a large one. The evidence is often visible — a crack, a broken outlet stub, or a canister hanging out of position with its strap corroded through.

Overfilling is the mechanism people do not expect. Continuing to add fuel after the pump clicks off pushes liquid into a canister designed only for vapour, and liquid fuel breaks down the charcoal and can split the housing. A canister replaced without changing that habit fails again, so it is worth mentioning to the owner. Check the canister's filter and vent valve while it is off, since both sit in the same debris.