Cooling system mystery
So, as I mentioned in the "Lots to sort out" thread, the bike has generally been behaving well. One exception has cropped up, however, and that is with the cooling system.
The bike seems to run at normal (for this bike) temps. During long idles, the fans turn on at 220 and, temp immediately begins to come down and fans shut off about 208. While cruising, the temp is anywhere from 180 - 205. My problem is with coolant recovery. The overflow tank fills itself up, but does not draw the overflow back in to the radiator and ultimately pisses some coolant overboard. In fact, The system seems to stay pressurized LONG after the engine has cooled down (I'm talking after DAYS of not running). Literally a week after the big ride to Tellico, I popped the radiator cap and it blew off positive pressure! Meanwhile, the overflow tank is completely full and levels in the radiators and definitely down.
My first instinct was that the cap was either malfunctioning or perhaps the wrong one, but if the system doesn't generate a vacuum as the engine cools, then of course there's nothing to draw the coolant back in to the system, regardless of the cap. Anyone have any ideas on what might cause this? Maybe I should try a new cap anyway? Kinda stumped...