Hydraulics opinions

I have a 1949 8N with suspect hydraulics. I have changed over to an naa piston and o-ring. I have replaced the relief valve, cam follower pin, adjusted the linkage with Zane's adjustment jig. I dropped the pump and cleaned about 1 1/2 inches of goop from the pump housing, and still have the problem. The hydraulics work fine when you first start working the tractor, but as it warms up they get weaker. The right side seems to start getting weaker, putting more pressure on the left, and after a couple of hours it will hardly lift anything at all, bush-hog, disc, blade or any implement. I have checked for leaks, but found none. I think that the tolerances in the pump are such that it just can't pump the fluid when it gets hot. Is it time to rebuild the pump?
Should the innards of the pump be rebuilt, or should the pump and chambers be reuilt? Thanks for you opinions and suggestions. Your help has been much appreciated.

Rick Sisk
8n 245054

This is true if the N pump is not cracked. If it is cracked then nothing but another pump housing will help

I came up with a new idea the other day to check a pump for cracked housing. Remove the pump from the tractor and tap the pressure outlet hole in the pump to recieve a 1/4 inch pipe thread. Then install a grease fitting in the pressure hole and start pumping on the grease gun that is connected to the fitting. You can increase the pressure until the safety relief valve starts to exude grease. If you do not see any grease comeing out from a crack somewhere then the pump housing is OK.