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2004 Lincoln T/C

Service Engine Soon light came on. Code read: slight evaporation leak…Anyone have any suggestions what to look for?

Make sure the gas cap is tight.


+1 to Tester’s recommendation.
Then, drive the car for several “drive cycles” in the hope that the light turns off.

If the light doesn’t turn off after…let’s say…5 drive cycles, then you need to look at things like the evap system’s purge valve and the lines running to it and to the carbon canister.

At 10 years old, depending on climate, vacuum hose connections can crack and leak. The diagnostic system can sense this kind of leak and set a code. The vacuum lines need to be inspected and any cracked connectors or lines need to be replaced.

Good comments above. The EPA requires newer cars to use the engine computer to test the evap system periodically . The evap system is supposed to be air tight. b/c if it leaks, raw gasoline vents into the atmosphere which is an air pollutant. Plus it makes your mpg’s lower, so the owner has an incentive anyway to fix the problem. As you drive the car extra air above the gasoline in the tank has to be allowed in to replace the gasoline used, but no gas vapors are allowed to escape the other direction, so all in all it can be a pretty complicated system, with various purge and vent valves, some one-way, some two-way, even the gas cap is a complicated contraptions these days, any of which can fail.

Replace fuel cap with Motorcraft brand FC961. If the light does not go off on it’s own after a week of driving then have a mechanic perform an evap leak test to see what is leaking.