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.

 

[Barry Bowen]

There is no way to turn off the 3pt. As long as I have the 3pt raised all the way, I have enough for the loader as the leak then is very minimal.

See if this helps figure things out. If I lower the hitch half way and it finds it's spot to stop, I can push the end of the arms down another 3-5 inches and then it will bounce right back up. Does this help with the diagnostics?

 

[J_J]

How about a gate valve or solenoid valve at the input to the 3pt valve. That will shut off all hyd to the 3pt, and give the loader all the fluid and pressure.

One guy on TBN just took his 3pt valve apart and found some bad o-rings.

Locate a parts/service manual and you should be able to break it down and repair it.

There is a spot on the 3pt valve that is the neutral position, where no fluid is supposed to flow. If you raise the lever up, the 3pt should rise and start to relieve at the end of the stroke. .

If you had a gage install, you could see this point when in neutral.

 

[Barry Bowen]

There is no way to turn off flow to the 3pt. It is inside the castings. The priority valve bolts to the trans housing, and the flow to the 3pt is internal from there.

The plan is to rebuild both the cylinder and valve. I was looking to see if any one had any good insights. It is my belief that when things got way way over heated this summer when I was having problems in the steering that I damaged or blew out orings or seals in the valve and cylinder. Chances are they have never been apart since the tractor was new anyway.

What things do I need to look out for on the technical side of doing this particular valve and cylinder. I have the shop, hoist, and tools to do what ever needs doing. I have rebuild hydraulic valves before. I just did the MCV pump and valve on my 706 yesterday, but I think this 3pt valve will be much more complicated then that. I have access to the shop manual no problem, infact I should be getting it this evening.

 

[jenkinsph]

I am still suspecting the valve and would also add the position control linkage has to rotate to move the valve to the center (no flow) position.

If the rockshaft will hold an implement in the up position for an hour or so without dropping down I would think the rockshaft cylinder is okay. If it were bad enough to cause the problems you infer it would come down instantly when you shut down the tractor.

Does the position control work properly? If it isn't the valve would not be moved to the nuetral position. Not familar with the 1520 setup

 

[jenkinsph]

There is no way to turn off flow to the 3pt. It is inside the castings. The priority valve bolts to the trans housing, and the flow to the 3pt is internal from there.

The plan is to rebuild both the cylinder and valve. I was looking to see if any one had any good insights. It is my belief that when things got way way over heated this summer when I was having problems in the steering that I damaged or blew out orings or seals in the valve and cylinder. Chances are they have never been apart since the tractor was new anyway.

What things do I need to look out for on the technical side of doing this particular valve and cylinder. I have the shop, hoist, and tools to do what ever needs doing. I have rebuild hydraulic valves before. I just did the MCV pump and valve on my 706 yesterday, but I think this 3pt valve will be much more complicated then that. I have access to the shop manual no problem, infact I should be getting it this evening.

Before going inside I would check all the external linkage adjustments on the outside. There are several adjustments outlined in the technical manual that are critical for proper operation.

There is a remote possibility that some of the failed Oring is lodged in the system too. If you have to remove the top housing and rebuild the valve and cylinder I would check on the cost of a new transmission pump while you are at it. I had to change one in my 4020 many years ago and it wasn't too costly, better than taking it all apart again.

 

[Barry Bowen]

All the linkage on these is internal. I would do the trans pump now, accept it requires splitting the tractor, so I will be waiting to do that until I have to do the clutch in a year or so.

 

[Tx Jim]

What is IIRC and RS?
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.

Barry
If you have flow by lowering the 3pt then you may as well resolve yourself to remove rockshaft housing and replace RS valve o-rings and I'd also recommend replacing RS piston o-ring & thermal relief valve.

Here's a list of the parts required but PLEASE have parts person double check my list of part numbers before ordering parts.
2-T17882 RING,SEALING ADD 1.40 USD 2.80 USD
1-T21641 GASKET ADD 12.75 USD
2-R10093 PACKING,O RING ADD 0.84 USD 1.68 USD
2-R31136 RING, BACK-UP ADD 0.99 USD 1.98 USD
2-L55204 ORING View/Update 1.07 USD 2.14 USD
1-AT21781 VALVE,THERMAL RELIEF ADD 49.45 USD
1-R65621 PACKING ADD 5.46 USD
1-R65620 SEAL ADD 13.25 USD

 

[Zebrafive]

IIRC= If I Recall Correctly
RS= Rock Shaft

It sounds like you have leakage internally in your Rock Shaft Valve.
When you have the arms fully raised and the valve in the raised position, I think the valve being shifted, the oil flow dead ending in the rock shaft cylinder, you get enough flow to operate other hydraulics.

I would rebuild the valve. I would also rebuild the cylinder since I have it a part. I do not think your thermo relief valve is at fault, but would replace it too, since it is a part.

The trans oil pump can be tested without splitting the tractor. JD dealer should have a flow tester to do this.

 

[Barry Bowen]

Here is a link to the JD site for a rebuild kit for the cylinder and valve for 1520.

http://jdpc.deere.com/jdpc/servlet/...vlets.HomePageServlet?search=model&model=301A


I am already resolved that all this has to come off. I got a hold of the shop manual from my uncle yesterday, so I can read all the details on this job.

I also see the complete valve seal kit ar92385 (instead of separates)
spring f3322r
spring r49684

your prices though look about half of what is coming up on line, where are you getting those so I can go there and get stuff instead.

 

[Tx Jim]

Barry
The part # ar92385 you listed if I'm looking correctly doesn't appear to contain all the parts I listed. These 2 part numbers aren't shown(1-R65621 PACKING ADD 5.46 USD,1-R65620 SEAL ADD 13.25 USD) plus this one(T21641 GASKET ADD 12.75 USD). The prices I listed are from my local JD dealer that I log into to llook up parts. Some dealers charge MSRP and some charge MSRP plus a % markup.