more on 1486 hyd problem

ok. 1486 that all hydraulics get weaker as oil warms. i changed filter,cover seal and gasket. i did the air pressure test in the transmission and found no leaks. i overfilled the trans with 7 gallons of hyd oil. but yet all hydraulics are weak. when at idle i get 800lbs of pressure at the rear outlet but when opened wide open i get around 2200lbs. the 3 point lifts slowly unless i open it up and the steering is hard to turn unless i open it up a little. the light in the dash comes on also. these problems came on all at once so i figured its a suction problem but i cant seem to find any problem. any more ideas? thanks joe

Before i would make any guess on your problem i would have to run a Flow Rate on the whole system and also see if the oil is getting over heated. As to a suction problem , when ya changed the filter and gaskets did ya have a problem getting steering and brakes back??????? if not then it is not a suction problem .

I would check to see if the o-ring was blown between the pump mounting plate and the rear case.

Your tractor has two mostly separated hydraulic systems. It starts with a common source from the pickup tube through the filter. After the filter the suction side of the pumps are separate. Filling an extra five to eight gallons of fluid will cover any areas that may be leaking on the suction side.

There are two areas where the 86 series tractors differ from the earlier ones. First is the long dipstick tube in the back to check the oil. If the tube is bent down inside the tractor the actual fluid level may be much different than indicated on the stick.

The other area is the supercharge line and it again connects the suction side of the pumps. It is designed to reduce the amount of oil flow through the filter. Oil from the rear pump is routed up through the hitch and to the auxiliary valves. If neither the hitch or the auxiliary valves demand any oil, the return flow is routed to the suction side of the front pump at the bottom of the MCV assembly. If there is demand for oil, the flow to the supercharge is cut off so no unfiltered oil returning from the auxiliary valves is allowed to enter the suction side.

The reason I think your problem is with the supercharge line is because you said it came on suddenly and affects both hydraulic systems. A crack in the line can allow air to enter without leaking oil out because you have the demand for oil from both pumps but are supplying oil only from the rear pump. There should never be pressure in the line, only suction.

A crack at the end of the line under the fitting may allow a metered amount of air to enter. Since the amount of suction on the line will not vary significantly from low idle to high idle the volume of air entering will remain nearly constant. The amount of oil demanded by the pumps will nearly quadruple from low idle to high idle. As a result the percentage of air in the oil entering the pumps will be much lower at high idle and account for the better performance at higher speeds.