I noticed some smoke coming out of the valve cover vent hose when my Kubota B7100 was running (no oil coming out and not moisture) and confirmed that there are actually slippery “black substances” in the coolant. I have removed the radiator cap after starting it and it is not bubbling (it just “stirs” a bit). The tractor emits whitish smoke when turning, but this disappears within seconds of turning it on. It’s a little hard to boot, but this may be a weak battery (haven’t checked that yet).
The cooling system is a thermosyphon, so there is no pump. The water circulates by gravity; hot water rises and cold water falls creating a circulation within the engine and block. There should be a whistle at the end of the radiator cap vent hose that starts to whistle if the engine starts to overheat. The radiator fins must be kept free of grass clippings, etc. White smoke when starting is usually unburned fuel, so check the spark plug function.
If you don’t know how to test the heaters, don’t remove them or connect them to a 12-volt battery. Buy a cheap multimeter and a test light for about $ 20. Then he asks again for more help to understand the GP test procedures shown in the workshop manual. Before suggesting you have serious problems, some basic things need to be done like a thorough cleaning and rinsing of the coolant. The engine oil and filter need to be replaced. Transmission oil and filter. With the new fluids on the full brand, you can now observe any change in the level of any of your engine oil, transmission oil, or coolant.