After reading up on a number of threads regarding fuel vapor smells/leakage - particularly Mike Romain's postings - I decided to give a shot at replacing the filter at the bottom of my canister while I was doing an oil change over the weekend. Picked up a replacement filter from Napa (part #2998 - Filter Breather) for about $3, pulled the canister up and flipped it over and was initially stumped as to how to remove the old filter. It quickly became obvious one simply pulls it out past the plastic molding across the canister bottom. Mine wasn't attached or held in place by anything other than that molding (a lip around the edge of the canister bottom and a thin bar across the middle).
At first I just kinda poked at the old filter (which was filthy) and then I set the canister back down, upright, to answer a question from my wife. At that point I heard an odd sound which turned out to be the charcoal running out of the canister all over the ground. Apparently I'd shifted the old filter to the side just enough to create a hole.
So I cleaned that up, put the charcoal back into the canister (about a cup's worth), installed the new filter and all seems well.
My question: is it really the case that the filter is just held in place the way I describe? Or is mine perhaps missing some screws or some other retaining mechanism to make it all more secure? Seems like it would be easy for a branch or something to poke up just right and catch that filter, pushing it aside just enough to allow the charcoal to all fall out.
Here are the old and new filters:
And here's the underside of the canister: