Fordson new super major low hydraulic pressure

I recently bought a new to me Fordson Super Major (Ford 5000 Diesel) because I couldn't passup the price for a running tractor with brand new tires on the rear. However the hydraulics were not working when I bought it. After diagnosis I found that the PTO clutch plate had come apart so the hydraulic pump wouldn't run. I split the tractor and installed a new drive clutch as well as the PTO clutch and those are now working great! However I could not generate more than about 300PSI and as such the tractor won't even lift the bushhog that I bought it to run. I have had the top plate off and everything SEEMS to be in working order but I did notice that the unloading valve only had the remains of it's o-ring. So thinking that was the problem I tracked down the correct part number for the correct o-ring for the unloading valve and reassembled. Now I can generate 500PSI but that is still a far cry form the 2500-2700PSI that is specified in the manuals. I have ordered all new o-rings and a new service control plate gasket as well as a new top cover gasket and valve cover gasket so I will be pulling the top plate yet again :-( in the next two or three weeks. Does anyone have any suggestions on what I should be looking for? Just about the only things I have not looked at directly yet is the pump itself (because it does pump so I don't think it is split), the filter cartridge and the backpressure valve.

The unload valve works without an O ring but if you do not fit the proper Ford O ring you will be in trouble, so it is good that you have fitted a correct one. I would still leave the ring off or fit the later unload valve that had a metal ring.

Did you check the pressure on the auxiliary service port?

Do you have the original auxiliary service plate with a flow control? If so, the flow control valve may be stuck. I have had to free one off only a month ago for a friend. It is a fairly easy job. Take the auxiliary plate off, on the back is a plug, held in by a roll pin, it has a screw into the gallery but do not worry about that yet. Drive the roll pin out then you have to get the plug out which may need you to drill and tap a small hole into the end, put in a small screw and lever the plug out. This is the official Ford way.

Once you have removed the plug, there is a spring, remove this. The valve will be stuck at the bottom of the drilling.

I made a piece of dowel rod and just tapped it in to the hollow rear of the valve itself. It needs to be tight as you are trying to rotate a stuck valve. A little easing oil of your choice will help. Once the valve will turn, try rotating the dowel between your hands as if you are grinding in valves. I have also used a battery drill on the end of the dowel to spin the valve and move it up and down the bore. You will find the screw mentioned earlier will stop the valve coming right out but once the valve is moving freely, you have no need to completely remove it.

The pump is the other area that your problem might be. You can get it out by removing the three mounting bolts and, with a wriggle, pull it off the two dowels that locate it. We used to do that without draining the oil, working by feel.

Once you have the pump out, before stripping down, mark the outer housing to ensure it goes back the right way round as you need it to be reassembled in the correct direction. Then remove the gear and D key. I have found that the gear has often come loose and sheared the D key. Then take the end plates off and check that the large O rings in both are in good condition and not blown. Replace rings and reassemble.

I used to love working on the hydraulic systems and trouble shooting on them when in the dealership.

I put a pressure gauge on the auxiliary port and that is where I was getting the 500 psi. There seems to be plenty of flow back to tank so I am fairly sure that the pump is good

I drove that pin out and pulled the plug but there was only a spring in there and I did not find a valve Inn there. It sounds like that is my problem, that basics being stuck at the bottom. I will pull the auxiliary plate again and try your dowel trick. When I got the tractor I did all the fluid and filter changes that one always does when getting new equipment and the hydraulic oil had probably 3 liters of water in it when I pulled the drain plug.

Thanks for the suggestions I will take another crack at it in the next few days and report back.

Thanks
Mike Somerville
simervillefarm.com

I couldn't wait so I pulled the auxiliary plate today and the valve was stuck. It didn't take much to unstick it though. I have resembled the plate and now the wife wants me to go with her somewhere so I won't get to put the plate back on until tomorrow at the earliest.

I will report back with the results.

Thanks,
Mike Somerville
simervillefarm.com

Just reporting back. That valve spool was stuck so I unstuck it but I was still having the same issue. I pulled the top cover again (my lord that thing is heavy and unwieldy). When I had the cover off I figured I would just go over everything because I didn't want to do this again. I pulled the pump so I could get the pressure line off as well as the return line and back pressure valve out. I replaced the filter because I could and the old one was very done. I found bits of o-ring jammed in the back pressure valve so I cleaned all that up and then I noticed that the o-rings for the pressure line were shredded where they run through the casement of the tractor. A new pressure relieve valve on the lift cylinder because it was available, cheap and why not as well as a new top plate gasket and all seems good right now. I was able to lift a counter weight I have here on the farm and it wouldn't even TRY to lift it before. Today I will try and hook up the brush hog and see what it can do. Thanks for all the help lad(s).

Back in the day, I and my apprentice would have those lifts off and serviced probably two a day, all without the aid of any lifting gear. One farm we went to on a regular basis, they had a lot of tractors, had a giant Swedish manager called Ove, you would ask him for a lift with the top and he would wrap his arms around it and before you could even start to lift he would have it off. The standing joke was, as he lifted it, he would say Brian, you are not lifting !!

You sound as if you have covered all bases, the pressure pipe O ring can be easily cut and trimmed as you drop the lift down if it is a bad fit in the pipe grove, a little oil or grease is always a good thing and, again, a genuine ring helps and, yes, I have done that myself a couple of times over the years. ;0(