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I'm voting for either cracked head or blown head gasket... most likely between #2 and #3 cylinders for either. If you're losing that much coolant, its not leaking externally, and there is not a lake in the floorboard of your truck; you're pretty much left with an internal leak of some kind. The bubbles upon shut down can be a sign of this as well. Time to run a compression test.


Agreed. You say that the head has been replaced in the recent past, was it replaced with a new head, or a junkyard piece? If it was junkyard, there's a chance that the 'new' head is warped as well, unless it was carefully checked. Even if the head is solid, if the head gasket was damaged during install, or mis-installed, you could be experiencing a leak as well.

Out of curiosity, do you know how much coolant you put back in when you originally flushed it? That would at least give you a ballpark as to how much potential air in the system you would have to burp out.

James