The Stovebolt Site Forums The Shop Area Engine Shop bypass oil filter -- check valve?

I have a 3800 with 216 egine, all original. I see the bypass oil filter stays full of oil.

That must mean that there is a check valve in the return line to keep the oil from draining back?

Or does it mean the return line is really blocked and no oil is flowing through the filter?

Which is it, or what else keeps the oil in the filter can when engine is not running?????