Just to save yunz some trouble, seeing as how it got me twice. When encountering a no heater or an overheat on a 544J with a 6068 motor, odds are that the impeller has dislodged from the water pump shaft. Deere uses a plastic impeller. To easily verify, remove the pressure cap from the expansion tank above the radiator and start the machine. Circulation occurs, regardless of temperature, in that tank. If down a couple inches, you will actually see a stream of coolant entering from the opposite side, into the reservoir. Also of note, the heater hoses never get hot, and, on a machine at operating temperature, the temperature drop across (down) the radiator is nearly a 100°F. One ran a full year (summer and winter) with no overheat (convection + hydraulic fan), but had zero heat in the winter. Also of note, a reman water pump is only $40 less than a new one.
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