[7tango7]

Hello group. New to the forum. New to JD ownership. 1988 JD 420 tractor. Having problems with the control valve used to raise and lower snow blower attachment.

When I first got the tractor this summer, I noticed whether running or not, the lever control to raise and lower front snow blower would travel from the neutral position to UP and return just fine. It would NOT move to the down position. At the time, I ignored it, as I was busy mowing grass, not plowing snow.

This fall, I attached the snow blower and found the same problem. This time, I was a little more forceful with the control leaver and it seemed to "free up" and work OK, although it still did not move as freely as the other two control levers.

Unit sat idle for about 6 weeks. Then back to same old problem - lever would move to UP, but not to DOWN. Again I got a little forceful. This time, the control valve went into the DOWN position and stayed there !

I have not yet begun to disassemble anything, but have done a little testing. (please forgive my layman's terms for the following parts). None of the linkage from the control lever to the control valve body seems jammed. The cylinder sticking out of the valve body that the linkage connects to seems jammed into the valve body. That is, it appears to be stuck in the fully depressed, DOWN position. Gentle prying upward will not free it.

Before I go tearing things all apart, I was hoping someone might know what's causing the problem and suggest a course of action. Also, if you know of anything to beware of when removing / disassembling the control valve body, I would appreciate hearing about it.

I can take some pictures and post them, if anyone would like to "SEE" the problem.

Thank you in advance for any assistance you can offer.

Tango

 

[MXZRXP]

I can take some pictures and post them, if anyone would like to "SEE" the problem.

pics can usually help clear things up...

 

[7tango7]

Have added two pictures - hope they are sufficient. Size of file pretty restricted in this group. If anone wants larger pics or higher resolution, please E-mail me or tell me where I could post them with a link to them from this thread.

Also disconnected the linkage between the control valve and the control leaver. Lever moves freely and valve is still stuck in the DOWN position.

Thank you,


Tango

 

[TUDOR]

You cut off the picture with the valve body right at the problem area. I'm guessing that there is a can covering the end of each spool at the bottom of the valve body. Remove the offending can and dump the water and other junk out and put it back on.

The valve body on my FEL never gave me problems like that until the temperature went sub-freezing, then I had to melt the ice to get the can off. It seems to be a summer/high humidity cause. Winter never had the same issue.

I could be wrong, but the symptoms are the same. If that spool won't go down into the can, that's where the problem lies.

 

[TUDOR]

Oops! I just noticed that the spool is already in the can. Probably physical damage or something hung up in there. The can needs to come off in any event.

The other possibilty is 'O'-ring failure and a piece is stuck in the passages preventing the spool from moving. The can needs to come off for that one too.

 

[Team_Green]

Tudor ... What is this can you speak of???

 

[ddelle338]

It also may be something as simple as rust/crud built up on there. See if you can spray a little kroil or blaster on it (where the shaft slides down into the valve body) and then let it sit for a bit. Come back and see if you can move the handle back up. Then clean it with some steel wool and rags.

 

[TUDOR]

Tudor ... What is this can you speak of???

I'm not sure about this valve set, but most valves have a cover over the spool at the opposite end from the control lever. This cover is usually a can shape with lugs to screw it down with.

Since it sits vertically, it makes a good catch-all for fine particals and condensed water vapour. It covers the return springs and retainer for same that are located on that end of the spool. A broken spring or a retainer that comes loose has the potential to jam the spool in any position. Although usually that happens when the spool is in the 'neutral' or 'out' position, it's possible to seize it in the 'in' position as well, as this one is.

I'm not saying that is the problem, only that that is where I would look first. It's a mechanical issue with the spool and under that cover or can is where you have to start the disassembly process.

If there is no can, I'd have to see it to know where to start. Maybe a plug on the either or both ends.

One other possibility is debris from the system getting hung up in the spool. To check that, remove the hoses and eyeball the spool through the ports. That's a lower probability unless every other thing checks out okay. Then the question is "Where did that debris come from?".

 

[biker3777]

I had one that was stuck,just had to take it off and remove the plunger and clean it,never did SEE anything that would cause it to stick.

 

[THEPATRIOT]

One on my 140H3 was stuck,even though it looked ckean too.I used some PB Blast and worked it back and forth for a while.It popped and works fine now.

 

[PA318Guy]

Since it looks like you levers have "return" to the normal position I would agree with the others and tell you to use PB blaster on it and work it to see if it will loosen up before you try tearing things apart. On my 318 when I got it my levers were sticking where the rod goes through the side and I used WD 40 on it and it freed up!

 

[biker3777]

On this one I have now the levers were bonded in with rust,after I got them out I put a grease cert on the side so I lube them.

 

[7tango7]

UPDATE :

Thanks to your suggestions, I removed and disassembled the valve body. See pictures by following link below:

http://s233.photobucket.com/albums/ee148/Scotty_T_Steam_Fitter/JD 420 control valve/

As TUDOR thought, there was rust and scale in the cup and on the spring at the bottom of the spool on the problematic control valve. No water though.

Getting it cleaned up and reassembled was enough for today. Tomorrow, I'll reinstall the valve body. Anyone have any suggestions about getting air out of the hydraulic system ? Is it as simple as hook up all the lines and refill the hydraulic resivoir ? Do I need to "burp" or purge the air out and if so, how ?

Thanks again to the group for the helpful responses.

Tango

 

[TUDOR]

Once it's back together and sealed up, start the engine and cycle each of the cylinders full stroke 3 or 4 times and you should be good to go. Any valves with no actuators can be left alone until they have an actuator plugged in, then the same process applies. Good practice to get into every time you start the tractor after an actuator has been changed or hooked up as well as any time the tractor has been shut down for even a day, especially in the winter.

Unless you had a big spill, I doubt that you lost enough oil to affect the reservoir. Check it though, in case it has been depleted over time.

 

[7tango7]

Once it's back together and sealed up, start the engine and cycle each of the cylinders full stroke 3 or 4 times and you should be good to go. <snip>

Unless you had a big spill, I doubt that you lost enough oil to affect the reservoir. Check it though, in case it has been depleted over time.

Thanks for the reply, Bob. With my experience on large machinery hydraulics, I figured it would probably be a case of cycling all the rams.

Will update the group, once I get the unit back together and running.

Tango

 

[biker3777]

These are an open system,big stuff is a closed system,hence no need to"bleed"

 

[TUDOR]

Big systems are bled because of the sheer volume of air in the lines and actuators. Several hundred feet of 3" to 6" piping and multiple cylinders with a 30" bore and 4' stroke need a lot of fluid. You don't really want to do the cleanup when that slug of air under pressure comes back to a 10000 gallon reservoir.

For small systems like on GT's and SCUT's, at most you're dealing with a gallon or two of fluid for the entire system, excluding the reservoir. Even including a FEL's cylinders and lines, and with a correspondingly smaller pump pushing the fluid, the backsplash when the air comes back to tank is somewhat less dramatic.

Open circuit or closed, the previously mentioned procedure applies in a small system. All hydraulic reservoirs are vented and this is one of the reasons why.

On a brand new small system, a couple of squirts of oil in each of the actuator and pump ports is suffficient to lube the sealing surfaces until the oil arrives from the reservoir.

 

[7tango7]

<snip> Unless you had a big spill, I doubt that you lost enough oil to affect the reservoir. Check it though, in case it has been depleted over time.

You were correct, Bob. only lost about 1/3 of a cup during disassembly. When I finished repairs and replaced the fluid I'd drained, the level was still in the sight tube, so I didn't bother to replace the bit I'd lost. BTW, for those wondering, I did put back in the SAME fluid I took out beacuse i had done an oil and filter change a couple months ago and the tractor had not had an hours use since, so the fluid was virtually brand new. normally, when I would do such a repair, I'd replace the "used" fluid with new.

Tango

 

[7tango7]

UPDATE : <snip> Getting it cleaned up and reassembled was enough for today. Tomorrow, I'll reinstall the valve body. <snip>
Further update: My appologies to the group for not updating sooner. Seems like there are SO many things to do on the acreage while I'm off work and before it turns cold. Anyway, I got the tractor back into service the next day and all is working fine. I deduced that the "cup" at the lower end of the spool (with the 2 screws, springs and ball bearings), is the mechanism that holds the spool in the "float" position. I was not able to clean the 2 ball bearings very well, so the action of the control valve going into FLOAT is not QUITE as smooth as it COULD be, but seems to work adequately. I will get some new ball bearings an install them in the future, but its not a priority just now. I doubt I'll even use the FLOAT function, as I will be snowblowing on level pavement.

Again, I would like to thank those members of the group who responded to my inquiry.

I'll be working on some new brackets, to allow me to move the cab rearward on the tractor from its current location. One I get that done and the tractor all set up for winter, I'll post some pics, as the group seems to like pics of each other's tractors.

BTW the reason for moving the cab - as it is now, the seat has to be fully forward for the cab to be attached. While I CAN get into the tractor, it is not at all comfortable this way. Having the seat back a couple of inches will help a lot.

Tango

 

[etc02]

The same lever on my 420 is not very smooth and tends to stick. Is it possible to remove the cap, clean and replace the ball bearing without removing the whole spool, or is it easier to just remove the spool?