My cooling system works fine, but it strikes me as overly complicated. I don't know why they built it the way they did, and I wonder if I could simply it.

The one problem I do have is that the coolant level in the billet AST / thermostat housing seems to randomly flucutate by an inch or two, which trips the coolant level warning.

Any ideas of what might be causing this? Is the sensor simply placed an inch or so too high? I don't seem to be burning or leaking coolant, and the level in the overflow is usually at "full."
Maybe I just need to bleed it? In which case, how should I bleed this system?

If I was to refresh the system, do I really need to use a 1.3 bar cap?

Could (or should) I get rid of the swirl pot?

On an unrelated note, my car is finally street legal in Japan! (It only took me a decade to get around to it.)