I am known to digress...
And to correct discrepancies...
I did both in the last. You should have specified Indiana and not let it open to misinterpretation by others. I knew Michigan was not it, but others did not. I educated them.
It's not a matter of 'do it and see what happens' your incessant overthinking of the source of the water and postulation has proven fruitless.
If you are so set that you MUST disassemble the engine to find the source, you OBVIOUSLY have FAR more time on your hands than most adults.
My solution after your already exhaustive FRUITLESS investigation is to propose you can overthink this all you want...but you WON'T find the problem that way---as you have already proven!
Now is the time to turn it over and FIND THE SOURCE.
FYI: "cars, buildings, bridges, and atomic bombs were designed this way"
They WERE. That's the point most deskbound engineers forget. They postulated, but IN THE END, after all the thinking and postulating in the world...they had to DO IT to see if the calculations were correct. Many times they were at a loss to figure out why they were not.
A nice example exists outside the town of Terragona (sp?) Spain, where great Roman Acuaducts still exist. During a failure of a local Nuke Powerplant a piece needed to be transported to the plant from the local port. There were two bridges to choose from: One newly designed, with state of the art materials and a theoretic weight capacity far exceeding the weight of this heavy-lift replacement component. The other, a Roman Arch bridge still in use today, over 2,000 years old, but of absolutely unknown weight capacity.
The decision was made, for safety, to use the Roman Bridge.
All the fancy engineering in the world is useless when a practical expedient alternative is a known quantity and speeds up the process.
The Company Diesel Technologies in Grand Rapids existed solely to test nut stack configurations in Unit Injectors. Why? Because for all the calculations in the world, all the theory, when you put them in the REAL WORLD, some just didn't work. One of the most VALUABLE TOOLS they utilized were test technicians who spend thousands of hours a year assembling and testing these systems. Diesel Technologies valued their input, as many would make a suggestion about configuration which yielded results. You couldn't quantify why beforehand with calculations and theories, but not trying it because it didn't fit the calculations was not a way they operated. And as a result the invented and patented things other companies coveted. In fact, so much so that PCM Bosch bought their Commonrail Technology. But they were a German Company, and if the injectors didn't test the way they calculated, then the test must have been done wrong. Bad attitude, nonproductive. Move south were guys were less prone to argue and just do what they were told.
Problem solved. Development slowed.
The world doesn't run from behind a desk, on theory. It runs by running. You can vacillate all you want, try to understand it...but you are obviously missing the fact that everything you have checked proves no way for the glycol to get where it currently resides.
The two alternatives are:
Continue Postulating, and guessing, and disassembling something here and something there without a CLUE how or where it's coming from.
Start the vehicle, make PRODUCTIVE OBSERVATIONS, and then SOLVE THE PROBLEM.
As you will recall, Trinity Site was EXTENSIVELY INSTRUMENTED. If they knew what was going to happen, why instrument it? Perhaps to refine the calculations? That's called PRODUCTIVE OBSERVATION.
An equivalent to this situation is this:
Had The Manhattan Project Engineers took your stand, they would still be there, LOOKING AT the bomb they conceived, wondering if it would work.
Contrary to your postulation, they eventually realized that they have 'to do it and see what happens'---you will recall there was a question if this would ignite the atmosphere, and later with the H-Bombs crack the atoms of the Ocean.
They overcame their fears, they 'did it to see what happened' and then OBSERVED SCRUPULOUSLY the results.
The big thing here is your definitive postulations and hypotheses earlier will conclusively be found incorrect if you do this. Perhaps this is your fear....but inevitably, for lack of productive evidence elsewhere, this is, I propose, the ONLY practical avenue of continued investigation to conclude this matter.