4640 issues with aux. hydraulics

SlimTech

New User
4640 is having issues with the aux. hydraulics.

The tractor is being used with a feeder, when the door to the feeder is opened the hydraulics are allowing the door to shut and not keeping it held open, as if the cylinder is bleeding off, but it does not do this on any of the other tractors so I know its not the cylinder.

I was asked to repack the implement valves when I showed up, I never got to see how the tractor acted beforehand. The implement valves on the back of the tractor were disassembled and resealed,none of the seals were blown inside the valve as was originally suspected, there was some sludge inside the valves that was cleaned up as best as possible but other than that no issues that I could see. The cylinder bleeds off no matter which valve it is hooked to.

TIA, Slim
 

Welcome to YT
Sounds as if one or more of the 4 poppet valves(key 16) is leaking. These valves are available from YT parts for $31.25 each by clicking on John Deere at the top of this page.

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As Jim stated the poppet valves are leaking past their seats or they are out of adjustment. I can Re-build and bench test them here if you would like to ship them to me, they will be repaired correctly and tested to make sure of it..
[email protected]
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(quoted from post at 04:17:29 02/24/17)
Welcome to YT
Sounds as if one or more of the 4 poppet valves(key 16) is leaking. These valves are available from YT parts for $31.25 each by clicking on John Deere at the top of this page.

45987.jpg

So it would not be the seal (12-13) that is leaking then?

My thought is, if 16 is leaking wouldn't that have likely messed up the bore inside the valve or no? Is it not tight like a valve spool?

Thank you for the response.
 

Thank you for the response!

Trying to get this repaired on my own though if at all possible, of for nothing else than the experience.

Is there a way to tell if the poppet valve is leaking by a visual inspection? I recall them all having quite a bit of build up in the lands on them, tried to clean all of that as best as possible, apparently not well enough.
 
I feel not so intelligent now, after looking at those poppet valves closer, it's the seat that is actually leaking isn't it? That material is made up of something softer that seats inside that valve right?
 
Yes the poppet valve has a nylon seat that will erode or get small pieces of metal embedded into them,, mail me if you want and I will tell you about it..
 
(quoted from post at 13:31:01 02/24/17)
(quoted from post at 12:20:21 02/24/17)
Apply shop air . If it hisses in the closed position, it ain't closed.

Apply shop air where???:lol:

Tx Jim that why you need the shop manual from you friends at Johndeere.com or whatever. :oops: :oops: :lol: :lol:
 
(quoted from post at 14:58:56 02/24/17)
Apply shop air where???:lol:

Tx Jim that why you need the shop manual from you friends at Johndeere.com or whatever. :oops: :oops: :lol: :lol:[/quote]



Checking scv poppet valves setting with air wasn't discussed in last JD tech manual I read.
 
I agree Jim, air testing is not discussed in any JD manual but I do an air test before putting them back on the tractor. (because I don't yet have a test bench like Tim S). I put a male coupler tip in each receptacle and put shop air in the pressure port on the top front side of the valve housing. With the valve in neutral there should be no air movement through the coupler, when moving the control lever in each direction there should be air on one side then the other as the lever is moved the other way. If this all tests good I then install it on the tractor and check it with a gauge. If I recall the book at this point, you should tweak the lever to get 1500 psi on the gauge and it should maintain this pressure (within 100 psi)for about a minute. It should neither drop OR rise.
 
To add to this "Hillbilly Tech" ,,wait to install the dust covers/disc on top of the couplers and mix up some dish soap and water in a spray bottle and spray each side down as you pressure it up, and down around the spring and keeper looking for bubbles,, it will give you a hint of a leak,,check the free travel on each cam too,,you want to have about 3/16 to 1/4" free travel (you will need to go in through the side and loosen the screws up a bit so the cam can adjust)..at the end of the lever too much here and you will have too much travel in the guide up near the handle,,too little and it will leak past when it warms up. Most shop air is only 160psi, but it may give you a hint of it all going right. I do this before I set them on the test stand, there they get warmed up and pressured up to 2250psi, I then dry then off with some brake clean and look for leakage.
 

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