Here are a couple of my old posts on the NAA lift Hope this will help. First thing you need to do is befor starting the engine take out the bleeder plug at front top of the piston pump. If their are a lot of bubbles comes out first before the oil becomes free of bubbles you may be loosing prime. If not then you have a sticking or imovable unloading valve in the lift.
You need to be sure that the big flat O ring that goes between the backpressure valve and the right side of the lift is good and not leaking when you take the lift off.
Do you know the procedure for removing and replacing the lift in relation to the backpressure valve@ the acorn nut etc.?
Pull the plug that is over the unloading valve with the threaded hole provided and push the unloading valve out with a pumch etc.
Replace the O ring attached with the Ford Part #NCA 836 B or the current replac ement number O ring and nothing else.Not a parts house O ring.You will be sorry!
Polish up the unloading valve with 180 grit paper and hone out the bore with the same on a pencil or dowel wraped with sandpaper.
Thanks for the praise! I like that!
The 20 w oil probably would not have any effect on the operation of the lift unless it could have in some way caused the O ring on the unloading valve to change shape. The 134 oil is what I would use. However you guys who are where it goes down to 0 deg probably could use a lighter oil better.
I would first try bleeding the pump by removing the front pipe plug with the allen head hole in it. Start the tractor and let it idle as slow as possible and when all the bubbles are gone stop the tractor and put the plug back in. You will loose about a half cup usually so put something under the pump to catch the oil.
If it won't work then you must go into the lift and take out the unloading valve and clean it up and replace the O ring with the Ford O ring made specifically for the unloading valve. The old part # was NCA 836B. Don't use a substitute or you will be sorry.
It is a good idea to replace the back pressure valve or at least acertain that it is working properly.@ has some resistance to air pressure etc.Also be sure the big O ring that seals the back pressure valve to the side of the lift is in good order.
The back pressure valve must be disengaged from the side of the lift housting inside by removeing the large arcon nut on the right side of the lift housing and backing the large hollow screw out counter clock wise till a light resistance is felt. Stop unscrewing then as you will damage the valve if force is used past when you feel resistance.
The unloading valve is coverec by a plate at the front of the control valve housing just above the control valve. Their is a plug over the valve that must be pulled by inserting a bolt with fine threads into the plug and prying it out with two bars. The valve can then be pushed out with a punch of the approiate size. Don't strike it with a hammer. The O ring will be on the unloading valve that needs to be replaced.
If you will look around on the other reference pages of the N board etc you can probably find some good views of the lift to give you some idea of what you will be looking at.
When taking the lift control housing off the tractor remove only the bolts that are around the ;outside edge of the housing and do not remove any of the bolt that are inside this circle of bolts. If you encounter a bolt that has fine threads on it put it back where you took it out. The fine bolt hold the cylinder to the cover housing.
Good luck Zane in Al.