QuestionQUESTION: Hi.I have a case ih mx110 tractor that has a bucket loader attachment.The tractor worked fine until last week, when the power steering stopped working all together. Rock hard. Strangly, the sttering works fine when the bucket is operated, but not on it's own. Did a bit of rerearch and found out that the hydraulic system runs through a priority valve. Took it out, cleaned it all up(found nothing obvious wrong).Took the steering pump out,(cleaned and also nothing obvious worng with it).Put it all back together,no go.Took the "signal" hose off at the priority valve, and tested. When the steering is in neutral, no oil from hose or priority valve. Same when i try to turn the wheels-no oil from either side.When I activate the bucket, no oil comes out of the steering hose, but squirts oil from the priority valve and the steering works.Put it all back together-no go.Is the oil supposed to come from the steering pump to the priority valve when I try to turn the steering wheel?or visa versa? Please help.
ANSWER: I don't know if your loader is hooked up to a joystick control valve or through the tractor's remote valves, but you probably have a bad signal check valve in whatever valve is operating the loader. On a pressure flow compensated hydraulic system, the hydraulic pump is variable displacement and only pumps on demand. The signal lines to the pump compensator tell the pump to build pressure when oil is needed, and how much pressure is needed to do the job. There are signal lines coming from the steering, remote valves, and 3 point hitch so that when any of these are activated, it tells the pump to start pumping. There are one way check valves in these signal lines so that when one function is operated (the steering for example), the signal pressure does not bleed off through the other signal lines (remotes and hitch). If a signal check valve is stuck open or has debris holding it open, the signal pressure can't build for the other functions until the function with the bad signal check valve is operated. That's why the steering only works when the loader is operated. The signal check for the remotes is in the fitting where the signal line attaches to the remote valves. Remove and inspect it for debris, damage, or a broken spring. Not sure where oil should squirt out when turning the wheel, I've never tested it that way. I usually cap off the signal line at the remotes and if the steering works, I know I have a bad remote signal check.
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QUESTION: Thanks, here is the latest. When I put a pressure gauge on the hand pump(Steering pump) pressure/supply line, and leave the tractor in neutral(started), then I get 250psi. I then moved the pressure gauge to the top of the priority valve(too test pump pressure in neutral) and I get 400psi.when i try to turn the steering wheel, the gauge moves up to about 500psi.(Should I be getting the same at the steering pump?) Does this mean that there is an internal leak in the priority valve? or maybe the compensator is not set correctly?(what should I be getting at these ports? Thank again.
Answer The pressures are not normally checked at these locations so I'm not sure what the results should be. I'm guessing that the 400 psi that you are getting is probably low pressure standby. This is the pressure that the pump maintains when no functions are being activated, and is normally checked at the hydraulic pump. If there was a leak or something else wrong with the priority valve, the steering would probably not work at all even when using the loader. I still think you have a bad signal check in the remote valve.
