The fuel vent line on most Cessna single engine aircraft attaches to a check valve inside the tank to prevent fuel from flowing out of the vent line, but this valve has a weep hole that allows some fuel to pass to prevent pressurization of the fuel tanks. Unfortunately, this weep hole is much lower than the fuel level of a full tank. Fuel will continuously leak out of the vent line until the fuel level is below the weep hole. With the original vent line, you cannot fill the tanks without wasting a lot of fuel.
The Cessna heritage aircraft also have a tank interconnect vent line that allows fuel from both tanks to leak out of the vent. When parked on an unlevel surface, the fuel loss from these aircraft may be many gallons.
McFarlane has solved this problem with a redesigned vent line featuring a unique hump that rises above the top of the tank. Some fuel can still escape through the weep hole and out the vent to prevent pressurization of the fuel tanks. However, fuel will stop leaking once the pressure is relieved, and the tanks will remain full.
Kits with a new connection hose (where required) and rubber grommet are also available where applicable. Just add a "K" suffix to the part number.
For ordering information, go to Fuel Vent Lines.