Thanks for the encouraging words. You’re right, it was probably leaking coolant before that morning startup. First objective when I start digging in is to find the coolant leak. I just want to know what failed there. Fans are in good operating order; mech fan passes the newspaper test and the electric fan seems to operate normally. The coolant pipes under the intake are only about a year old and the hoses all looked intact, so my money is in the expansion tank or radiator.

I worry about head warpage mainly because I do not know how long the temps were so high. I did not have the presence of mind to glance at the coolant temp gauge until I shut the engine off. The engine developed a knocking sound right before I shut it off; could have just been detonation?