There should be a bleeder on the upper radiator hose? SR have it, KA might?
Make sure you remove that bleeder when filling coolant/water.
next, only use distilled water 100% during diagnosis, so you can spill it anywhere.
When finished and problem is solved, use only
distilled water +
antifreeze.
Never use tap water.
Okay now, diagnostics. Do a compression test because its quick and easy. make sure you got no blown head gasket.
Take the rad cap off and run the engine from cold start, since there is no thermostat you should be able to see water flowing constantly and getting warm pretty fast. make sure it doesn't have a bunch of bubbles forming which could indicate a blown head gasket. I put my finger in the water to feel it heating up but be careful if you do that. The top of the rad should be hot or be getting hot as the engine runs. If the water up there stays cool and there is no evidence of flow then obviously the water pump isn't moving water. The system is very simple, water pump moves water and rad cools it. ez
and here is a warning about hot coolant. That shit will burn you, the skin right red off. So ALWAYS gently squeeze the radiator hose before you remove a cap to see if there is pressure in the system, and ALWAYS be aware that at any second the system could violently erupt, a hose could pop, a fitting could burst, etc... and hot water will boil you alive. IMO wear extra protection around a unknown cooling system, a face protection, eye protection, arm and hand protection, treat it like fire.
finally you really need a thermostat and a controller for the fan. Run an engine cold and it will eat engine bearings and cyl wall up. Oil needs to be 200*F to 220*F and the coolant needs to be at LEAST 170*F IMO (168* to 210*F is fine)
