It's hard for me to tell from that video whether that's releasing positive or negative pressure, and the way this thing is plumbed I'm not sure what to expect out of the coolant level in either case. I'm not near my vehicle so I can't check mine for you.
Any sign of white smoke on startup? Any other symptoms of any kind? If you're feeling really squeamish about things, a compression test would help alleviate some concerns, more than likely. You could also do a leakdown test on the coolant system (pressurize it artificially when cold, see how it holds the pressure). Then look for that white smoke on startup to see if it forced coolant into a cylinder.
The other thing that I suppose might cause this is if your system isn't fully bled. A pocket of air somewhere expanding and contracting with the temperature change might contribute to more of this than in a system where there was zero air.
FWIW, it would not surprise me or alarm me to see some pressure differential after 12 hours of cooling as long as there is no clear loss of coolant, no white smoke, and no overheating or puddles on the ground.
Any sign of white smoke on startup? Any other symptoms of any kind? If you're feeling really squeamish about things, a compression test would help alleviate some concerns, more than likely. You could also do a leakdown test on the coolant system (pressurize it artificially when cold, see how it holds the pressure). Then look for that white smoke on startup to see if it forced coolant into a cylinder.
The other thing that I suppose might cause this is if your system isn't fully bled. A pocket of air somewhere expanding and contracting with the temperature change might contribute to more of this than in a system where there was zero air.
FWIW, it would not surprise me or alarm me to see some pressure differential after 12 hours of cooling as long as there is no clear loss of coolant, no white smoke, and no overheating or puddles on the ground.
