overheating when plowing and the coolant system

I have a 1959 Fordson Dexta 3 cyl. diesel. I tried plowing with it in the wrong gear (3rd low) but it overheated and steam started coming from the radiator. I let it cool off and drove into the barn. It did not overheat when I just drove it around. I drained the coolant and flushed a tiny bit with some water and then filled it with coolant/water. I have checked the thermostat and found out that someone had already removed it! The radiator fins are fine and clean. I have filled it completely up with coolant and there is no air in the system. The temperature gauge is broken. I then took it out and tried plowing with it again to test it under load. This time it did not overheat at all. Some coolant came out of the overflow hole under the fill cap, but I have heard that is normal if you have filled it all the way up. The radiator hoses and the water pump got a little warm and you could tell that it was slowly warming up, but nowhere near overheating and it handled plowing fine. Can I assume the water pump is OK? Remember there is no thermostat. Should I install a thermostat and how important is it? How do I install a temperature gauge? It looks like I need to raise the fuel tank. How do I do that nd is there another way? What is the result of driving it without a thermostat? All advice and help is appreciated. It is very important to me to restore the tractor and have it working correctly. I also rely on it for my hobby agricultural production with plowing, harrowing, etc.

Up here in Minnesota a Diesel engine needs the thermostat in winter. But if you are plowing now, you must not have winter.

Some engines the thermostat helps keep them cool. If the water circulates too fast, it doesn't have time to cool down in the radiator, and other
odd situations.

But it isn't usually too bad to run without one. I wouldn't be worried about it. If it were me I would put the proper one in, it was designed for it,
might as well have it.

I would be concerned about the broken temp gauge. That should be replaced as soon as possible. You are not able to know what is going on
without it. Replace the gauge!

Engines can run a long time a little hot.

They get destroyed pretty fast if they run a lot hot, or too hot for a long time.

Paul

As Paul said below I would worry more about the broken temp gauge than having a thermostat. Bob

Wrong gear will not cause overheating as long as you are not laboring the engine.

Pros and cons I have absorbed over the years on thermostats is that they slow the flow through the system forcing better circulation in out of
the way places in the block that would otherwise go uncooled, or inefficiently cooled. Diesels tend to need a higher opening temp as they run
cooler (less combustion energy lost to heat), especially in winter, like 185F vs 165 sort of thing.

I know on outboard engines, especially V types where the stat hole is lower than the top of the block, with no stat (stat hole open to the outside
world) the top of the cylinder in the right hand (looking from the rear) bank of cylinders doesn't get covered with cooling water because the
block doesn't fill with water at the mid to lower rpms.

So, my consensus is use them.

On the overflow, years ago there was no coolant recovery and no AC to cause high temps in coolants in vehicles containing passengers. The
normal recommended coolant level was just over the top of the fins. As the water or water/coolant solution heated, it expanded and filled the
tank. Filling to the top was a waste of money as the excess would just be vented out the overflow tube.

Along comes hot engines and coolant recovery systems, and fill to the top to force the air out of the radiator and 50-50 mix because a higher
concentration of coolant didn't cool as well as plain water but plain water had it's drawbacks with rust and freezing and water pump lubrication
and all so the 50-50 has been pretty much standardized along with pressure caps to force the system to tolerate temps approaching 250 F and
remain intact. My 2011 Silverado has sequential electric cooling fans, no belt driven fan, and the temp gauge sits rock solid on 210F (212F is
boiling at sea level.).