If I am driving around the city or long distance in cold weather, I have absolutely no issues. If I'm making serious climbs or driving on the freeway in hot weather, about an hour of driving will cause overheating. The reason I'm overheating is because the radiator has an excess of steam built up which then pushes it into my overflow reservoir and from there it spits out until my radiator no longer has enough coolant in it and I have to pull over, let it cool, give her a refill and then its good to go for another hour or so (in a strenuous environment). But then the next day, cold and rain? Well, for example, I drove it from Santa Cruz to Seattle in the rain without any issues.
I have been driving this thing regularly for 2 years with this problem. Including driving from NW Washington to Southern California and back TWICE. Probably not good for the engine, I know... The last time I drove home from San Diego I took Highway 1 the whole way, which at that speed and coastal temperature I had minimal issues. I-5 through California in the heat? Forget it. I'll be out of water every 45 minutes.
What I have done: In this time I have changed a couple hoses, replaced the thermostat (with an OEM), swapped the radiator cap, and had a local radiator guy who owns the same van diagnose my radiator and do a full flush with some stop-leak. He doesn't think my radiator has any cold/hot spots and thought it was fine.
I have not changed: The fan clutch, most of the hoses nor have I personally tried doing a full system bleed/re-fill. I'm unsure if the radiator guy bled the system or not, but he was passionate about helping me.
I watched that video about testing the fan clutch to see if it engages or not and I honestly cannot tell if mine does. I watched the video 10 times and tried it myself (right after it overheats, I popped the seat and gave it some gas while the needle was nearly at the H and I feel like I don't notice as severe of a "whine" sound as the one I could hear in Tim's video) But the fan speed does seem to increase with the throttle. I couldn't hear a clear activation though. It seems to have the loud noise when starting it up cold like mentioned in the video.
When I do overheat and I pop the radiator cap off, steam rushes out (and also my overflow) for a good minute or so. Then while I add more water too it, it gurgles as if there are tons of bubbles in there. I'll top it off, squeeze a couple hoses and then all of a sudden I can add another quarter gallon of water.
I also have no other head gasket symptoms such as coolant coming out the tailpipe, loss of power, milky oil, and the coolant doesn't seem to have oil in it either.
Other than this, the van is in fantastic health.
------ BACKSTORY ------
I bought the van from the original owners. They had recently got a compression test which came back flawless. Right when I went to meet them the first time they called and said something went wrong. A week later they called me and said the water pump went out while they came to meet me and they had to get a new one installed. Is it possible the new water pump has been giving me this issue? Or, was there nothing wrong with the water pump in the first place and it was a failed diagnosis?