NAA hydraulic pump prime

I was once given a pump that had new bearings, new seal, new shaft and a new valve and spring kit with new pistons. Everything that you can put in a pump. I thought boy this is going to be a piece of cake. I put it on my tractor and couldn't get it to do a thing. I took it back apart and made sure the seal was not installed backwards etc. All seemed right. I put it back together and same no work. I put it on the shelf and it laid there for several years. Then one day I took a complete new set of gaskets out of a kit and realized that one of the new gaskets had a cutaway that would allow the oil to bypass the valve if used in the pump I was working on. After I finished repairing the present one I took the pump off the shelf and took it apart and this time I took the valve plate off the head of the pump. Sure enough the wrong gasket was installed with the by pass cut into it. I put the correct gsket in it and sold that thing for $400. Worked perfectly!

Zane

I had to bleed my 1954 NAA piston pump quite a bit after the rebuild. But since bleeding it initially, I have not had another problem. Open the plug until just a few threads are engaged, run the engine at the lowest possible RPM until nothing but oil squeezes out between the threads of the plug. Get a big pan underneath there - it is messy and will take quite a bit to get all the air out.

Good luck,
Dan