Well, I pinched off that line, and even tried several pumps on the other two, and on all three off the side of the reservoir I'm hearing fluid go into the overflow tank on the passenger side. I got them pinched off with vice grips as much as I comfortably could without eating into the rubber- they were sealed off. I don't understand.

But I think I found my leak anyway by more careful scrutinizing and am going to go update my other thread on that specifically... drainage is dripping from the middle of the car, and I'm seeing active seepage from the 1" hose coming off the bottom of what I believe is the thermostat housing. My radiator and other hoses look fine and no bulges, but there's a small coolant puddle underneath that theromostat assembly.

 

There are two 5/8" hoses that run under the intake manifold and connect to the "Norma connectors" on either side of the octopus. The drivers side norma is the one you are looking at. The air intake manifold needs to come off the change that one.

The 5/8" water hose running under the manifold on the passenger side connects in the front with the plastic water manifold. It is easy to see and you can get that one w/o removing the air intake manifold.

 

Just an update on my leak. I changed out the top radiator hose, along with replacing the old clamps and it seems to be good now. I took it for a 15 minute ride with outside temps about 100 F and it's back to the 200-202 F temp range.

No leaks after about 15 minutes of sitting, so if it is OK in the morning, I will top it up with coolant and call it fixed.

Will need to change the bottom hose out soon as it is getting pretty soft. Didn't realize how much until I compared it with the new hose. I also bought the bypass hose for the thermostat tower, but will save that effort for another day.

 

Well done, Mike! Glad that was it, knock on that beautiful wood.

I still have the pressure tester and adaptor and probably need to return it now that I've 90% certain ID'd the leak (heater hoses under the supercharger), but work, social engagements and a home landscaping project have sidelined my XKR for another week or two.