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Hydraulic pump cavitation

R

Rick Rauchle

Member
I have a 2640 that is still getting a cavitation in the main hyd. pump.The only time it cavitates is when I have aload on the three point.The filter has been replaced along with the sump screen cleaned.I have also rebuilt the rockshaft and scv valve to no avail. When I put the load down the cavitation quits. Is there an easy way to test the output of the internal pump and lines? I hate to split the tractor unless I,m really sure what the problem is.
 
Did you check the rockshaft control valves after the rebuild for leakage? This can be accomplished by looking in hyd filler hole with 3 pt raised,engine running to see that no oil is spraying. I presume this tractor has "no FEL".
 
No, I haven't checked inside of the filler hole after the rebuild, and whats FEL? I did notice that with the brush mower on ,when I come back the next week its sitting all the way down.
 
One other thing that I noticed, is that all the hyd. comp. seem to be getting extra warm after use.The steering column, rockshaft etc. I can't touch them for very long.
 
(quoted from post at 08:19:20 06/22/13) No, I haven't checked inside of the filler hole after the rebuild, and whats FEL? I did notice that with the brush mower on ,when I come back the next week its sitting all the way down.
Click to expand...

FEL is front end loader. Hot hyd components usually indicates an internal high pressure leak which contributes to hyd pump cavitation.
 
Jim, my 2640 does have a front end loader, and when the pump starts cavitating the loader will not operate very well either. I do have an electic destroker on the main pump, could that be leaking by causing cavitation?
 
(quoted from post at 09:28:54 06/22/13) Jim, my 2640 does have a front end loader, and when the pump starts cavitating the loader will not operate very well either. I do have an electic destroker on the main pump, could that be leaking by causing cavitation?
Click to expand...

Electric DS might be the problem. Try disconnecting wire. Does FEL loader have ind valve?
 
Jim, I'm not sure what you ment by an ind valve for the loader, its a 146 loader plumbed into the ported cover on the filter. It still cavitates with the loader disc. and off the tractor.
 

Some JD loaders are operated from the tractors selective control valves aka SCV's. Ind control valve is a spool valve either controlled by 2 levers or joystick. Some of the ind valves are convertible from open-center to closed center or vice-verse. The change over plug seal can blow causing closed center control valve problems. Disconnect the return hose from ported filter cover,plug filter cover,put return hose in bucket,crank engine with control valve in NEUTRAL if oil flows into bucket the FEL ind control is the hyd problem
 
Well I went out to where the tractor is today. I disc. the elec. destroker and put in a test gauge, I had 2000lbs at the high pressure outlet on the main pump. I looked in the filler hole with the brush mower on the ground and everything looked good, I then lifted it up, and I could see abit of oil dripping and lightly spraying to the right of the rockshaft lift cylinder. Its pretty hard to see where its coming from. When I rebuilt the rockshaft I replaced the spools and o-rings, found no cracks.
 
Yes, I still have cavitation when the loader and valve(all one unit)are removed from the tractor.Its attached to hyd.system with two quick conn.by the ported filter cover.
 
The pressure regulating valve down on the right rear side under the floor board could be giving a problem, I had one in here a while back that I had to change the valve "and" the housing to get things going...
 
(quoted from post at 22:28:52 06/22/13) The pressure regulating valve down on the right rear side under the floor board could be giving a problem, I had one in here a while back that I had to change the valve "and" the housing to get things going...
Click to expand...

Also the SCV(if equipped) could be leaking causing the spraying by way of the return hose but since no leak is noticed with 3 pt down I think your tractors problem are the control valves. Another possibility is that the clearance on the valves is set "too close). This can externally be adjusted by turning screw(parts key #2) through a hole in the rockshaft housing.
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