I have a 2004 Honda Civic thats new to me and just started overheating. I first noticed a month or two after I bought it...I was idling in park for 45min or so when I noticed steam coming from the engine bay and the temperature gauge reading all the way hot. It overheats the most when I slow to a stop or am idling and is less likely to overheat while I am driving faster than 40MPH or so but at times it will overheat and then remain at HOT for an extended period of time while driving at speed (I try to avoid driving in this condition obviously but I had to at the time).
I took it in and they performed a pressure test on the coolant system: came back fine; also have not observed white smoke from tailpipe and oil is not milky (suggests NOT headgasket problem I concluded). They didn't do anything to it and it ran fine for a day and then went back to overheating.
Fans: Both fans run when the AC is switched to on in the car. However, neither run (even when car reads as overheating on the gauge) unless AC is on (in which case both fans run but it still is overheated 5 min later). Since the car still does not cool even with fans running via the AC switch, I concluded there must be some issue aside from the fans not turning when the car starts overheating.
Water Pump: Not sure how to check this but after the car has been running from a cold start for 10 minutes the upper radiator hose is too hot to touch suggesting the coolant is being cycled out of the engine into the radiator. The lower hose is warm at this point but not hot. Earlier I was able to get hot air out of the vents with the AC turned to hot but I just tried again later today and it was still blowing cold at max heat on the AC dial, not sure if that means anything.
Hoses: In addition to what I observed above, there appears to be white splattered dried material (potentially evaporated coolant) on both the upper and lower hoses. Also when it does steam, it comes partly from near the upper radiator hose and partly from behind the engine (see vid).
Thermostat: If the upper radiator hose is too hot to touch at operating temperature, this must be opening so that cannot be the problem I would think.
Coolant Reservoir: At operating temperature when the fans should be on, I held a flashlight to the coolant resorvoir and it did not appear that any of the coolant had been sucked into the engine at all even though I believe it should have at that point. This was the case even though the upper radiator hose was too hot to touch. I don't understand this.
Gauge Temp Sensor: Seems to be working; slowly increases from cold start and steam comes out of engine after gauge has been reading all the way hot for a while suggesting it is accurate.
Question: Does anyone have experience with coolant systems to conclude something from all this information? The fan itself is clearly fine along with the relays and fuses for it since it is able to run, there is coolant in the car, and the one temperature gauge sensor seems fine. Do these symptoms suggest anything to anyone? I am at a loss and I am way to broke to let the mechanic figure it out by trial and error.
Pictures of oil, Coolant still in reservoir while engine at operating temperature, and video of steam while engine is overheating here (sorry it makes you download to view): https://ufile.io/f/1dx8l