Q: Vacuum sucking noise in a gas tank on a 2006 Jeep Cherokee Liberty when the car is turned off

You’d want to have your EVAP canister vent valve checked. Because when they break and stick, they’ll often do that and make the sucking noise. That is a Jeep, and when you shut it off, the EVAP system actually has a pump in it that runs the check release.

Sometimes those things will get noisy and if the lights don’t come up, then just ignore it. But, a lot of times it is an EVAP vent valve sticking and not working right and the pressure building up. Of course, what you might do is start by replacing the gas cap. The gas cap is part of the venting system, and if it’s bad, it can do that. The gas cap will cost you 10-15 bucks. I’d start by replacing the gas cap. It might solve the whole problem.