4020 hydraulic issue

[1938G]

I’m having hydraulic issues with a 1967 4020 with a synchro transmission and a 148 loader. The loader has always had a chatter in it until the tractor gets warmed up or unless we use it every day. We were using the tractor over the weekend and the loader suddenly quit working. We were able to drive it backwards to the house and had no problems with steering or brakes. After I got it home, I checked and it was low on hydraulic fluid and decided this was a good time to change fluid and filters and clean the transmission screen. Started the tractor and the loader still refused to move. Thinking it had air in it, I tried bleeding and still nothing. Checked the hoses to the loader and they were warm and the lines leading out of the loader spool were cold. I happened to check the three point, which we seldom use on this tractor, and they would not move, (whether this happened simultaneously or not, I do not know). Went to move the rockshaft control on the dash, and it will not move. Thinking perhaps the loader issue had some effect on the three point, I disconnected the loader and still the three-point refused to budge. I do not know what the pressure is in the hydraulics since I don’t have a way to test. Sorry for being so long winded, but wanted to supply as much info as possible. Any thoughts on the issue or guidance on fixing it would be more than greatly appreciated.

 

[Tx Jim]

I suggest to acquire a 5000 psi gauge with a JD hyd tip. I've seen that gauge setup advertised for under $50 which is much cheaper than a technician service call would be.

I suggest to check hyd pressure in front of & behind pressure control valve which is item 8 in photo below. PCV is located over rear of engine & in front of firewall. It's possible stand-by pressure is too low or PCV has failed blocking flow to scv's & 3 pt hitch. Stand-by hyd pressure should be 2250-2350 psi.