One of the most common questions I receive is concerning the power steering not working on 706- 1466 tractors. There are a couple of quick test to perform that will pin point the problem. First check to see if there is any squealing or growling noise coming from the clutch housing area. If there is then most likely the pto drive gear and or clutch pressure plate is stripped out and you are hearing the result of that. Here is a picture of one that is stripped and was squealing like crazy.
The pto drive gear is supposed to be turning the power steering pump but it is not. To further verify that the pump is or is not turning, engage the pto unit and raise the 3pt hitch arms or activate one of the remote hydraulic valves. If the pto runs and the hitch raises then the pto drive gear is not the problem. The pto drive gear drives the power steering pump, the main hydraulic pump(hitch and remotes) and the pto unit. So if the power steering pump is turning. Then
There are a couple of things that could be contributing to the problem. It may be that the tractor has been sitting for a long time. If this is the case then the fluid in the pump sump tube has drained back because of a small air leak in the sump tubing connections either in the filter area or at the rear frame and clutch housing oring. Check the gasket between the filter cover and the rear housing, if it is leaking air in the suction or vacuum will be lost and the oil will be allowed to run back to the reservoir. It may not be leaking oil externally because the leak could be above the oil level. It may be that the tractor has been parked with the front end sitting up hill. Making the air leak problem that much worse. It may be the outside temperature is dam cold. The hydraulic filter has not been changed in a while ( which could mean you have no idea where the filter is and you haven't ever changed it in the last 12 years that you have owned it ) Here is a picture of the filter housing
.These all are contributors to this issue.
If you have changed the filter and the fluid is in good condition we can move to more refined issues that can contribute to the problem. 1) You may be using too tight of a filter. I have found that Wix, Napa and Baldwin brand filters seem to be too tight and do not allow the hydraulic fluid too be sucked through when cold as easily as CaseIH or Fleetguard brand filters. 2) you may be using a universal type of Trans/hydraulic fluid. These tend to have a heavier viscosity than fluids designed exclusively for IH or CaseIH tractors.The heavier viscosity fluid does not flow through the filter when cold as easily as lighter viscosity oils designed for IH tractors. This being said there is no problem with any of these filters or fluids if they are changed regularly the temperature never gets real cold and the power steering or MCV pump is new or in good condition.From here on I will refer to the power steering pump as the MCV pump. (Multiple Control Valve pump)
Your tractors root problem is that the MCV pump is getting weak and is not developing enough suction when dry (because of a air leak stated earlier) from setting a long time or cold to draw fluid to itself and prime. The pump may still be developing enough pressure once it is primed to satisfactorily pressurize the steering ,brakes and TA. but it is becoming more and more difficult for it to self prime as it wears more. In addition to the MCV pump drawing oil to itself it has to overcome the potential vacuum of fluid being drawn through the same filter toward the stronger hitch pump. At engine start up both the 12gpm hitch pump and the 9gpm mcv pump are both drawing oil to themselves through the same filter. The mcv pump starts out at a disadvantage of 3gpm when both are new. Now add the wear factor,cold dirty fluid and filter ,possibly too thick fluid and possibly too tight a filter and that is about where you are.
The 86 series tractor came equipped with a "supercharge line" in an effort to over come this issue. The supercharge line feeds return fluid from the axillary / remote valves to the bottom of the MCV. This return fluid is from the main/rear/hydraulic lift pump(12,15 or 17gpm) and is intended to prime the MCV pump( 12 or 13gpm)
On the older models (06,26,56 and 66 series)you may need to replace the MCV pump if you want to correct the problem.Over filling the system with 5 gal of fluid may overcome the air leak by keeping it submerged in oil. Joe