I am new to ploughing and have a 1959 Fordson Dexta 3 cyl. diesel pulling a two furrow plough through a grass field. The tractor runs fine when driving around, but overheats when I plow a couple of furrows. I need help and have many questions. I assume the tractor should be able to plough through grass. The soil is sandy clay. Which gear should I plow with and how much throttle? My temp guage is broken. I will fill / check coolant levels, remove radiator cap and check flow. Is it my ploughing speed gear that is wrong or as I fear, the thermostat that is broken. How do I remove and check thermostat? All help or advice is welcome. I do not want to overheat and ruin the motor.