Well darn on that check valve. I will keep an eye on that bubble and see if I can get rid of it. I do the filter changes myself. I change the hollow bolt "O" rings at every fule filter change which I do at every engine oil change which I do every 10k miles. I have changed the screen with "O" ring quite a few times as well. Never a change to the symptoms when this is done. I have noticed this air bubble in the system before but it disappears instantly when I start the engine and I always just assumed it gets purged out when I see it disappear. I guess I will try to concentrate on getting rid of that air bubble.