A vent valve should not cause a leak unless the hose going to it is off or has a hole in it. I would visually go over the system to see if you find any hoses that are cracked or have fallen off. If everything looks okay I would replace the charcoal canister.
Below is a guide to help you see how the system works.
Let us know what happens and please upload pictures or videos of the problem.
Monday, February 5th, 2018 AT 11:00 AM