The great 2021 overheat event just keeps on giving!
Less than a week before the Michigan fall drive I started to see coolant running down the front of the motor. USB borescope camera showed that the weep hole was dry but found at least one hose clamp dripping. Excavated down in to the valley and found 6 loosened water pump & heater hose clamps and a flooded valley. These hoses & clamps were installed in 2018 and have had numerous leak-free trips the following years. I'm thinking the very high temp cycle cause them to sink in to the hoses and the clamps lost tension.
Tightened a few clamps, doubled-up a few, and swapped some thin band Norma clamps for thicker/wider Ideal Smartseal. Successfully held pressure for many hours and was all set to drive a few days before departure. Warmed up the car in the garage, went for a little drive, all is good.
Friday morning, 20 minutes out of town, coolant temp is holding rock solid at 145F. A tiny voice in my head reminds me of the "fail safe" thermostat also installed in 2018. FWIW the "overheat lock-open" feature does work, quite well.
Because more data:
-A new functioning thermostat gained 0.21 deg/s F, compared to a stuck open which gained 0.155 deg/s.