For hydraulic oil I buy the relatively cheap five gallon pail from Canadian Tire. The filler plug is located behind the seat on the right side of the tractor. For decades I was bothered by a persistent hydraulic oil leak from around the suction strainer (located near the operator's right shin) so I finally decided the leak was caused by the hydraulic reservoir becoming pressurized when hot. There may well be a vent to this reservoir somewhere but I can't find it and if there is one on mine it must be plugged. The suction strainer has an o-ring on it but is simply pushed into the casing so it doesn't seal well. The o-ring is an odd ball size and I couldn't find one in my area when I decided to fix this problem a few years ago so I replaced the filler plug with a venting pipe. I'll attach a photo below. This cured the leaking problem although I see that the o-ring is now available from Messick's for a whopping U.S. $8.16!
New Holland / Case IH: O-RING, Part # 74348R1
The level of the hydraulic oil should be just at the bottom of the filler neck with all your hydraulic cylinders completely retracted. Put the loader over a ditch or something similar to achieve this. The hydraulic system drain plug is located about a foot below the filler plug. I hope this helps.
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