D17 series 1 power steering temperature??

Better re-check it this morning to see if it fixed itself. It takes pump flow (up to 8 GPM full throttle) and a pump capable of making 1600 PSI if required to, to make the system work. Then, the control valve has to be functioning correctly, sending oil to either end of the steering cylinder when commanded to. Also has to be 5 quarts of hydraulic oil in the sump under the radiator being able to get to the pump.

You have a 1959 D17 with belt drive power steering pump

All pre-series 3 diesels were driven thru the generator, which wasn't a great idea by the pretty high failure rates of the connection splines. All early gassers were driven thru the governor. Again, not the best of designs as the governor gear works loose ruining the gear and shaft. Somewhere in that series 2 ?? gas vintage they came up with the belt driven pump. The series 3 diesels also got a belt driven pump. But, any power steering "kit" from A-C would have been old or new style design by what year the kit was put together. So, you could have a 1957 model with the newer belt driven pump if it was added on later in life.  Remember, power steering was always an OPTION, not standard equipment. Kind of like the 4-bolt WF on an old WD tractor.

Nope, it's a gasser. I checked the fluid level and belt tension (easy checks) and they are both fine. And when I first fire the tractor up the PS works as it should. Just once it has been running a while the power steering goes away and it's Armstrong steering! Which sucks since I have PS getting out of the barn but not putting it away which is when I REALLY need the assistance.