50 power steering

I got foaming oil in my ps. I have read that air getting in the unit will cause this. Any place more likely than others for air to enter,suction line between pump and pedestal or steering valve? Would this cause the wheels to lock up or drift to the left or right? I've tried setting it without success,this thing is turning into a night mare. I've read all the archives about the 2 cylinder unit and nothing helps. This unit was just recently overhauled. Anyone living within 400 miles of Raleigh NC want to tackle this,I'll be glad to haul it to you.

Air could be getting in from the pump ? was it rebuilt ?

The control valve acuating sleeve not being set up right or with uneven wear will cause the binding. Drifting to one side you need to center the valve housing. You loosen the bolts and tap it one way or the other. It takes very little movement to make a change.

Rob, Your foaming problem is more then likely the power steering pump. It normaly needs the bushings, seals and sometimes the main shaft replaced because of seal cutting.  You didn't say weather you have the original power steering or if it has been up dated with the newer 20&30 series adjusters. The locking up is usually caused by warn pins in the control sleeve (Replace the pins) And grooves warn in the steering worm cam and the pin groove on the steering worm on the first style power steering. If the cam groove is not worn too badly you can hone the groove out,I normally replace the cam. The same pertains to the groove worn in the steering worm. If the adjusting screw has not been replaced it will have 2 flat spots warn on it and no amount of adjusting wil work without replacing it. Before starting any of these adjustments start with removing the endplay at the worm. this is critical to both types of power steering control. In the newer steering the pins wear along with the helex on the steering worm and the cam this wear can be adjusted out, But you have to replace the pins in the control sleeve first.  Another problem on the late unit is when the steering has not been working properly and it has been forced to the right the ear on the worm side of the cam gets broken. If this has happened you will want to replace the worm or get it repaired. The only person I know that can repair the worm properly is Mike Williams in Iowa (563-212-9109).
Before you try any of the suggestions get ahold of a copy of the Power Steerihg manual SM 2050.
Be patient and start at the begining and do one thing at a time, This is not as serious as you might think.

Everything was rebuilt but not by me. The pump has a new shaft and seals and it was updated to a 520 steering valve,I'm not sure about new parts on the inside.I've tried tapping the valve gently and it seems to make matters worse. I have the SM2050 and also the original parts book. I'll pull the steering valve myself and go thru all the steps. The actuating sleeve has a good fit with the steering shaft,not sure about inside though. Something definitely not right. Thanks for the info.

Rob, Changing the valve to a 520 doesn't mean you have the late style. You can tell the difference if it has the big plug in the end of the steering worm. While you have it apart check for corosion on the spool valve, This will allow leakage causing drift in the steering.

Hope you used John Deere powersteering fluid. I found several problems such as you describe comes from using automotive fluid. It just doesnt hold up in them 2 cylds powersteering sys.

The JD ps fluid was used.