Consequences of a Faulty Gas Cap
A car’s fuel system requires partial vacuum in the fuel tank so that it can work correctly. A faulty gas cap will not maintain the necessary partial vacuum for the emission vacuum system to work correctly. This causes fuel to siphon out of the gas tank at the gas cap. The code for a faulty gas cap or other detected leak in the EVAP control system isP0442.
Dangers of a faulty gas cap
It is dangerous to drive a car with a faulty gas cap. Some of the visible liquid gasoline will change state to gaseous gasoline. Gas fumes are highly explosive.
It is also dangerous to park a car with a faulty gas cap inside a garage or other enclosed space. Gas fumes will concentrate inside the enclosed space. Turning on a light or making any other kind of spark can ignite them and cause an explosion.
Diesel fuel is not as explosive as gasoline. It is flammable. Leaking diesel also makes a road hazardous for other drivers.
Other consequences of a leaky gas cap
The emission vacuum system cannot work correctly with a leaky gas cap. This can cause more damage in other parts of the emission vacuum system. The car will also fail an emission test.
Other causes of gas overflow at the gas cap
Leaking gas from the gas cap can indicate that the gas line has a leak. Place a sheet of cardboard underneath the car to determine the severity and rough location of the leak.
Filling the gas tank to the brim can cause overflow. This is most common if you fill a gas tank to the brim in the early morning. Gas expands as it gets hotter. The excess gas flows out onto the ground through an overflow pipe. This is not a leak but it is also not good for the gas cap, the gasket, and the car. To prevent overflow, you should not fill a gas tank beyond the nozzle shutoff point.
A gas cap that leaks because of overflow will only leak when the engine is running. It will not leak when the engine is shut off. A gas cap that leaks for other reasons will leak when the car is parked.
Complications from leaking gas
Contact with fuel can deform the gasket. A gas cap cannot seal correctly with a damaged gasket. The gasket should be replaced at the same time as the gas cap is replaced.
Warranty
A leaking gas cap is part of the emissions system. This is covered by a longer warranty than most systems in new cars. If the car is less than 8 years old, the part could be covered under warranty.
