Top hose is pressurized by water pump when running. Bottom hose collapse causes overheating. That is why it has the wire spring inside it.
It has a new bottom hose too. The probably original hose sprung a leak recently. I caught it immediately as I was doing other under hood work. The spring inside still looked perfect so it went into the new hose.
After doing under hood work yesterday which involved starting it and stopping it several times, it was extremely collapsed this morning when I went to look.
It's a bit low on coolant in the radiator from the hose leak, the draining of it for replacement of all the hoses and not putting back in the worst of the coolant. I bet that's the problem, it's sucking in air, not coolant.
It was still below freezing at night until recently, so I couldn't do a cleaning flush at the time. I also just noticed that it has emptied the overflow bottle that I filled a month ago, so it seems to be functioning properly. At one time, the radiator was full too, but it probably has since purged more air in the system.
I'm currently house/pet sitting for a relative while they are out of town for a couple weeks, and I have use of their car and driveway, so I'm not driving it anymore until I do a bunch of work, including a full cooling system flush and refill with fresh Zerex G05 I already bought last month.
It seems to be remaining above freezing now, so I plan to drain it again and dump in two bottles of Blue Devil radiator cleaner that I got recently on sale. It calls for four bottles for the capacity of an IDI, but I don't want it to be too harsh, plus AutoZone only had two bottles left when the sale was on. Two bottles should still help. I will take it out for some driving to help circulate it, not just fill and idle.
I just need to decide if I want to spend $1/gallon for distilled flush water, or just buy 5 gallons of filtered water for $1 at an automated ice/water stand. (1/5 the cost). I really want to do a thorough flush until it's coming out clear.
Filtered should be way better than straight city water, which has a LOT of scale(?) here. My 1950s aluminum coffee percolator pot that I use daily to boil water gets a ton of it from the city water here. So much that you can make a small pile of it after just a few weeks of use without cleaning it. It's like a very fine sandy substance.
If there was space for a coolant filter, I'd probably add one, but seriously... in a van chassis, there's no room. Especially with a turbo kit! The water separator was put under the driver's seat with a hand/pull cable you accessed under a plastic hatch cover inside. I'd have to run 20 extra feet (10 in/out) of heater hoses way underneath someplace to mount a filter base. Maybe someday, but not right now.