Well went to N Georgia for the weekend 1 1/2 hours away. By the  time we got there, overflow tank was 1" from top of tank / ex pan tank was pretty much empty. Let sit overnite still the same in the am. At this point from past experience I must fill and bleed system to get coolant to proper levels or would fill to brim and spit coolant before I could get home. I am leaving overflow between min and max lines when I bleed/ have read the Bentley on how to bleed, and it does the same thing when I get it back from the mech. After a bleed depending on how much we drive the coolant starts to move from expan tank to overflow until it overflows. Happens every time within 300 miles of bleeding depending on how driven. Can drive around in town and at 50 or below and no problem. Could clogged radiator have created enough internal pressure to blow gasket? It sure had me chasing leaks for awhile before I fixed it. That is about all I can figure out..Have not visually inspected heater cores.That is all that's left. We are about to throw our hands up on this one.

Michael
89 Westy 
Rosebud