John Deere 301A loader and 3PH not working.

[medic0648]

I have a John Deere 301a that suddenly lost hydraulics. I previously had a local mechanic come out to look at it, they said the main pump was probably bad. I pulled the pump and took it to a local machinist that repairs hydraulics. they found the screen in the pump had crushed, otherwise the pump was good. I reinstalled the pump, tested the hydraulics, still no power, but now I have a pulsing hissing noise from the transmission area that speeds up as you raise the RPM. I do have 2500-2800psi just after the priority valve, but can't get the loader to actually lift, just move a little, and the 3ph won't lift with more than about 200lb on it. does anyone have an idea of what's going on and how to fix it. I also know there used to be a thread or 2 similar to this one, but haven't been able to locate it using searches. I'd also take it to a better priced mechanic, but don't have access to a trailer that can handle the tractor, and am working on a limited budget. also have a copy of the service manual, but it's not being too helpful so far.

 

[J_J]

With 2800 psi going to the loader, things should operate unless you have blocked off the return from the loader valve.

Closed center hyd system.

TractorData.com John Deere 301A industrial tractor information

 

[medic0648]

With 2800 psi going to the loader, things should operate unless you have blocked of the return from the loader valve.

Closed center hyd system.

TractorData.com John Deere 301A industrial tractor information

The issue with the return not working is that the loader and 3PH don't share their return line. And the test was at the back of the priority valve where the loader splits off from the 3PH supply. I'm trying to figure out if the OC pump went bad or the supply line is the issue. New symptom after the screen in the pump was replaced is intermittent hissing and no power steering now.

 

[jinman]

Medic, hissing sounds like a relief valve opening or stuck open. I would think that would effect your maximum pressure though. 2800 psi sounds pretty high, but without a system schematic, I have less than a SWAG.

 

[medic0648]

I think I found out what was hissing. It appears to be the priority valve opening and closing when the CC pump cycled. Found this out when I pulled the loader return line and it had hyd fluid flowing out of it freely. It appears the seals on the loader spools gave out completely and turned my CC system into an OC system. Will pull the valves tomorrow and have them checked.

 

[medic0648]

The update is had the o-rings in the valves replaced, tried the valve, still bypassing fluid. Tried to find parts to rebuild the Cessna valves, and there aren't any. Contacted JD and the local dealer wanted almost $1500 for a salvaged control. Got a 2 spool prince sv series valve and everything needed to make it fit for about $450 and the loader is faster and stronger than when the old 30gpm valves were working. Just have to order the joystick for the sv series to make things easier.