I've been saying squeeze the hoses. You can feel & hear whether there's air in there. Besides, even after using the coolant bleeder screw there's usually some air still in the hoses. I have to push down on the upper hose to push the air over to the radiator cap.

How badly does it need an oil change? You better just do it...

I bet you got air in the brake line for the one caliper that has a stuck bleeder. Murphy's law kinda works that way.