I installed a new fail-safe thermostat over the weekend. It worked for 24 hours, temps were 195-205 after the install.

Today driving home, both the realtime OBDII readout and the dummy gauge showed temps dropping steadily while at freeways speeds. Almost got down to 110. Temps were noticably low coming from heater core. Pulled into a gas station- > No leaks, and coolant levels are ok.

After 10 minutes, pull back on to the road, and temps get back up to the 195-205 range eventually. So the thermostat must have gotten stuck open, and the fluidyne kicks so much heat ass that underhood temps want to go to ambient.

What could cause this? Would a bubble in the system cause a thermostat to temporarily fail open? My last thermostat failed, by somehow warping itself, causing it to intermittently get stuck in the open position.

2gnt: '99 RS-T, killed by a toyota, pending rebuild...
Daily: Volt
Daily #2: '99 EVG ebike- STOLEN by PEDRO