John Deere 4020 Hydraulic pump

fordfx413

Member
I'm rebuilding a hydraulic pump for a friend, it is my first one my 4020 is next. The hydraulic pump is a 49cc 3.3. Im going through it cause he thinks its bad, but didn't do any tests before removing. Anyway.. I started to measure the pistons and there a little worn from spec, i measured the inlet valve lift and it is at .090-.1, spec is .82 i think. Just wondering how to replace those valves? and do they come as an assembly? The outlet valves look ok, and the shaft looks ok. I am going to replace the pistons and springs. Is there anything else that should be done while in there? What would the cause be from the inlet valves opening too far? Could i just leave them alone? Thanks for the help in advance.
 
Inlet valves are an assembly. They drive out.
They can't open "too far". They should not be removed
unless necessary. Feel for valve wear with oring pic or
similar tool.
Many times shaft, rollers and race will have cavitation
so should be disassembled and inspected.
 
OK. Thank-you. The inlet valves look good, and springs also look good. What is the best way to remove the bearings from the shaft? Also what is the best way to remove the bearing race from the inside of the pump?
 
hello, there are about 2 dozen loose roller bearings under the cam or collar in the middle of the shaft between
the two taper roller bearings. i use a bearing splitter to press off the bearing from the long end of shaft. if
you crack the big thrust washer just get another. more than 50% of the time you will find the shaft and rollers
are pitting on the cam. shaft & rollers need replaced. you can get the shaft from A&I thru deere if you ask for it
also important, remove the stroke control valve and examine the seat closely, if any question, replace. don't
forget the backup ring with an oring if you get a new stroke valve. you will probably need to adjust pump
pressure "2250" psi. on the tractor. don't forget the filter screen next door to stroke valve
 
Plan on replacing the pump shaft it will have a wear groove where the quad seal runs on it.
The thrust washers along side of the cam lobe should be replaced. Set up the shaft preload
before you put in the pistons. Get a new stroke control valve and crankcase outlet valve
and there is a screen that should be renewed on the crankcase outlet valve I think.
 
Ok thank you for your input. I will do some more checking tomorrow. Should I replace the taper roller bearings and races? I saw a little pitting in the race in the pump. What is the best way to get the race out of the inside of the pump? Thanks
 
A lot more than you expected right.
Many times I find it cheaper to just
replace the pumps.
 

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