oaklandish

I searched a lot and most overheating problems have the same symptoms but mine is a little different than anything I've found answered... occasionally my wagon will overheat. when it overheats I can see the coolant over-boiling into the reservoir and onto the street. It appears the coolant is not circulating well. I have disconnected the radiator at both ends and ran water through just fine. when I try to flush water through the engine only a little flow comes out the bottom. I believe the t-stat could be froze? the fans come on and the heater blows hot air as long as there is still coolant in the system. once it boils out not more hot air... when it is indicating it's overheating it doesn't feel any different than normal