@sting8282bird
I was having a lot of the same issue that you fixed. Disappearing coolant (no puddles), over heating after long stops, wild over heating while driving (inconsistent figured out it was air pockets reentering system). I also saw the price tag of a LIM gasket fix and had the response of "Nope, I'll do it myself." P0401 code was also popping up before hand. Cleaned out plenum and passage when I did T-stat a few weeks ago - now gone.
Actually just wrapped up the LIM last night, and verifying today that I got all the air out of the coolant shystem. Like you though, I don't believe my fans are coming on during the long stop lights or 5 o'clock traffic. ECT Sensor is new, t-stat is new, checked fuses, checked all three relays - haven't flat out replaced them - all checked out fine (audible click when car started). What else were you checking when you found your fan problem? I've possibly missed something I know.
Also did new spark plugs and wires - first time troubleshooting new plugs - never had an issue pop up afterwards, but getting a little bit of a rough idle. Feels like that "misfire lope" and noticed the front plugs were more challenging to get the right installation depth - I mention this bc wondering if overheating could have caused any warpage or seizing. I've seen other threads mention that before.
Thanks in advance.