640 ford lift problem

[Mike1955]

Does anyone know how to troubleshoot the pump on an old 640 ford tractor. I primed mine, disked about two hours using the lift. After lunch about an hour the prime was lost again. And it’s kinda shaken going up and down. Any help, I’ll be thankful for. Mike

 

[TractorTech]

Well, you have an air leak on the suction side of the pump most likely. I would look at the orings in the attachments of the hard pipe that feeds oil to the pump and pressurized oil to the rear case. Also, could be that the pipe bolts are a little loose, but you would most likely have high pressure oil squirting out.
Also, can we assume the oil level is correct?

 

[Mike1955]

Well, you have an air leak on the suction side of the pump most likely. I would look at the orings in the attachments of the hard pipe that feeds oil to the pump and pressurized oil to the rear case. Also, could be that the pipe bolts are a little loose, but you would most likely have high pressure oil squirting out.
Also, can we assume the oil level is correct?

Oil is fresh changed and full, thanks for checking simple first. I have bubbles coming out the plug on the pump when I remove it. I have the lift lever down I just think it’s getting air at the pump seal but I wish I could confirm it. Hate to work on it if it doesn’t need it. I don’t see any spraying or anything when I looked under the seat(looked in the place that I add hyd oil)

 

[TractorTech]

Sounds like the pump seal is the right diagnosis.