With those vents i think they have a small drain hole at either end under the front gaurds. If you have a build up of leaves and mud in there it will not be able to go through that hole. What i have been told to do with this is make a bigger hole using a hole saw in those ends under the front gaurds (you will have to remove gaurds) so you can get in there properly and give them a good clean. Just an idea. Good luck with it.