1520 3pt valve leaking, HELP

[Barry Bowen]

Actually the tractor is a 301A which is the industrial version of the 1520, so we can start from here

Tractor has closed center hydraulics to start. There is a high pressure leak in the 3 pt valve. I can tell because this is the only area getting hot when you start the tractor up and just let it run. No leaks in the steering or spool valves, no heating up there. As long as the hitch is all the way up, everything else works fine, but put the hitch down a little and the real leaking starts. Recently the hitch is starting to slowly go down some over night. It falls a few inches in two or three days. It will leak enough though that the loader will not work until I get the hitch all the way up again. It even effects the power steering, even though I replaced the spring in the priority valve.

How big a job is it to rebuild the valve and the cylinder? I have the shop to do it, and the capacity to lift the entire rock shaft housing off the tractor. What am I getting myself into doing this, and what do I need to really look out for?

 

[Tx Jim]

With engine running,3pt raised remove hyd oil filler cap and look inside for spraying oil. If spraying oil is seen ,rockshaft housing needs R&R. Not a major undertaking but lining up L/D control cam can be a challenge when replacing RS housing on trans case.

 

[Barry Bowen]

I looked in side it last night. There is no mist or spray, but as soon as I let the hitch down some, I see oil flowing. I guess this means start with the lift cylinder and go from there?

 

[jenkinsph]

Barry,
Sounds more like the rockshaft valve to me, so far I would think the cylinder is in good shape if the hitch will stay up. Could be the position control is out of adjustment too.

Curious if you have load and depth on this tractor?

 

[Tx Jim]

IIRC the return(lowering) valve dumps oil into sump when handle is pushed forward to lower 3pt. If no oil spraying is observed when 3pt is in the raised position then I think RS control valves aren't the cause of the heating oil. It is possible that the vales are adjusted to tight which can be adjusted from the outside of the RS housing.

 

[Barry Bowen]

I have done nothing to change any adjustments on the 3pt valve. Yes I have had load and depth control working perfectly fine. It was working as intended until this summer when this massive leaking and heating up started. Unless I have the hitch all the way up, I have to presure for any other hydraulic operation.

A contributing factor to the heating up was that the steering was leaking badly. An oring on the ram in the steering unit was basically gone. I repaired that mid summer, but I am wondering if the heating up from that did some damage to the 3pt valve or cylinder? I mean this thing really got hot to the point you could not touch the steering or trans housings, but I could not take it down as there was hay in the field that needed worked. This is my tedder and rake tractor as well as loader for round bales. Do you guys thing this could have caused a problem in the 3pt valve?

 

[Tx Jim]

Barry
Does loader have an ind control valve or does it operate off of SCV's? The adjustment I was referring to is to give the two RS operating valves sufficient clearance which is outlined in a JD tech manual.

 

[Tx Jim]

Barry,
Curious if you have load and depth on this tractor?

IIRC all JD 301's with a "3pt hitch" had L/D control.

 

[Barry Bowen]

What is IIRC and RS?

This tractor came from the factor with out any remote valves, no loader, and did not have a draw bar either. I believe it was a municipal mower. When I got it, I intended it for farm use so I got a draw bar out of the junk yard, and installed a two spool cross closed center valve. I got the filter housing for the return line and tapped into the proper spot down by the priority valve for supply. Valve has no detent or floats on it though, so these are not factory valves. I added a Westendorf loader about 5 years ago when I started doing round bales. Until very recently every thing worked fine, but over the summer this problem developed. As long as the hitch is up completely, loader works fine. With hitch leaver even lowered just a few inches, the big flow starts in the trans and loader does not work.

Recently after Irene here on the east coast, I had the 3pt generator on the tractor. With the generator on the ground, the hydraulic heated up FAST. 20 minutes and could not touch the trans. I undid the top of the lift links so I could raise the hitch with out raising the generator. It all settled down in about 30 minutes. Trans cooled off in the rain, 3pt valved cooled, but was still warm. Steering valves and remote were dead cold.

 

[J_J]

Barry Bowen,

Any leak in a CC system will bleed off pressure for the hyd system.

If you install a hyd gage in the system, you can monitor the pressure, and trouble shoot the hyd system.

If the 3pt lever is in neutral, no fluid is supposed to flow.

In the raise position, the fluid flows to the 3pt cyl.

In the down position, no fluid is supposed to flow, except the fluid that is released from the 3pt cyl.

You might check the relief valve for leakage.

So it sound like the 3pt valve is bypassing, causing heat and less pressure for the hyd system.

In a CC hyd system, the valves are in parallel.

Do you have a way to shut off the 3pt valve from the hyd flow? If so, then the loader should work normally.