Way back, my X was driving a Volvo 544 (B18), and blew a heater hose while driving to town (-35f). Of course the temp gauge shot up suddenly, but no steam from engine compartment (rupture was right at firewall, downward, and at those temps, there was always a big cloud of steam behind the car) she thought ' Damn temp gauge has gone screwy' and continued driving (about 20miles of running around, and back home). When I got home, I discovered the dry rad, replaced the hose, and refilled. I then ran the car for about an hour, and all seemed normal. However, 3 days later, she reported that the oil light had started blinking when she dropped the kids at school, oil was checked, and way over full, (mixed oil and coolant). The car was parked, and towed home that night. The next night, under a tarp, with a propane radiant heater (-40f) I removed the head, and had it trued, with a valve job too (95,000 mi). On re-assembly, I filled the 'case with a 50/50 mix of kerosene and good 10-30, with a new filter, and ran for 5 minutes. Drained, refilled with 50/50 mix, new filter, and ran 15 minutes. Drained, filter changed, refilled with good brand 10-30, and installed a mech gauge (which consistantly peaked over 80 psi hot). we finally retired the car 60,000mi later, only because the body got Swiss Cheesy, and we got a better one (same model).