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Repairing a leaking joystick control valve

willie59

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Here's a component that has been mentioned at various threads and folks have asked what kind of project is it to repair, the simple joystick control valve. From excavators to skidsteers, variations of this type pilot oil control valve are used on many machines nowdays, and the most common problem they have is leaking oil from the spool pistons at the top of the valve. It's typically just a tiny u-cup seal for the pistons causing the leak, replacing that seal is the challenge. I've repaired them inside the cab with hoses still attached, and disconnected from the hoses as well. I prefer to disconnect from the hoses and cap or plug the hoses so the valve components can be drained of oil and cleaned. Also, much more comfortable rebuilding while standing at a workbench than fighting one inside a cab.

My helper removed this one from a Case 9050B excavator because it was working all wacky, it was obvious someone had been inside this unit and had done something wrong. After he disassembled it, it became clear to me the former shade tree wrench had not paid proper attention to what they had disassembled and had not performed correct re-assembly, which I thought would benefit others as to what I found inside the unit, and to caution anyone who attempts to take one of these apart to note or mark the orientation of the valve mounting and every piece as to where it came from. I've repaired a couple of pilot valves, but I don't recall one being quite as specific inside as this one. This may not be that unusual though, so note how you take one apart.

This is a pic of the re-assembled unit, as I didn't have a pic of the unit when it was removed. You can clamp the body in a vise, put a wrench in the flats on the actuator disk, and screw the universal joint out that holds the retainer plate on the top of valve assembly. I have seen the u-joint installed with Loctite, making it all but impossible to remove it without destroying it, well, sacrificial part then, replace the u-joint.

9050B joystick valve 012.jpg

Once you get the u-joint popped loose, work very carefully unscrewing it, those brass piston guides have springs underneath them, if you were to simply remove the u-joint and retainer plate, the resistance of the o-ring seal of the piston guides would let go and parts would fly. Slowly screw the u-joint bolt out a bit, lift the retainer plate, and start working the brass guides up out of the chambers until the o-ring is unseated. Once they are unseated, hold down on the retainer plate and remove the u-joint, then you can gently lift plate off of the guides. Here's what you'll see when you get the plate off and the piston guides out.

9050B joystick valve 001.jpg

This is the spools and springs removed. The springs at top and bottom are the same, the spring to the right is different, and so is the one to the left.

9050B joystick valve 002.jpg

Also, the spring retainer disks on the spools, two of them are thick, two of them are thinner. Even the springs on the spools held in place by the retainer disks are different size.

9050B joystick valve 003.jpg

Differences don't stop there, the actuator pistons, the hole on the inside of them that the spool head fits into, two of the pistons have a 3/8" deep hole, the other two have a 7/16" deep hole. Hey, 1/16" makes a difference in how a unit like this operates.

9050B joystick valve 011.jpg

So the delima is, what part is supposed to go where? Fortunately for me, the Case parts diagram was a cross section view with excellent detail, even the parts list page noted which part went in which port, such as the thin and thick spring retainer disks. If it had been an exploded view, probably been bad. The one thing I couldn't determine was the main springs, the parts page told what spring went in what port by part number, but I had no way of knowing which spring was which part number, had to order new springs just to get the part number of each spring.
 

willie59

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Now that I have it sorted out how to assemble the unit proper, it's time to put it back together. First though, we need to discuss the leak that is common with these units. Replace the o-rings on the outside of the brass piston guides, and the seal that's in the bore of the piston guides. It's typically a small u-cup seal, or an o-ring with a backup ring. Very simple to fix a leaky valve once you get in there.

9050B joystick valve 004.jpg

The challenge to put these things back together is the springs trying to force the piston guides back out, you have to hold them set in the valve body until you can fit the retainer plate. It's nearly impossible to push all four spools/pistons into the unit using the retainer plate to force downward as you have to align each spool with the bore it fits into. You pretty much have to fit each spool/piston unit in one at a time and hold that unit in the valve body. There are various methods to do this, maybe some others here will post some ideas, but this method has been fairly easy and effective for me. Clamp the valve body in a vise. I take some thin/workable tie wire, twist a loop in one end and fit it around the outside flange of brass piston guide. I used a 3/4" socket sitting on the face of the brass piston guide to push the spool/guide assembly into the bore of the valve by hand. Once I push it home and hold it there, slack up the wire and tie it to fittings on bottom of valve. This keeps the spring from pushing the assembled unit back out. Make sure you have everything pulled taught, and have a good tie off on the underside.

9050B joystick valve 005.jpg

This is after all the units are installed and held in place with wire.

9050B joystick valve 006.jpg

Fit the retainer plate.

9050B joystick valve 007.jpg

Then screw in the u-joint bolt, stop short of fully tightening it, leave room to nip the wires and pull them out with some pliers.

9050B joystick valve 009.jpg

Now you can lock down the u-joint bolt. Check for proper contact of actuator plate on top of pistons, it can't be pushing any of the pistons down, nor do you want a gap between actuator plate and pistons. If adjustment is needed, put your wrench on the flats on the actuator plate, and another wrench on the joystick lever nut on top acting as a jamb nut. Pop the nut loose, typically RH threads, then turn the actuator plate CW or CCW to obtain proper adjustment. Lock down top nut, you're done.
 

Muffler Bearing

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Great Pictures and text ATCO! It's tough repairing someone else's repair. And it's a sickening feeling when you realize to late that you should have marked those pieces you just pulled out.
 

John C.

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I have had the same problem with the springs and had no parts drawing to relate to. I figured the weakest spring went on outside since that was the weakest way to push the handle. The next was to the inside and the heaviest springs were fore and aft.

It seemed to work the last time I did one. Also I've never had those things pop out on me. Usually I've had to use plier and a rag to pull the spools from the bores.

Nice job ATCO!
 

willie59

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I have had the same problem with the springs and had no parts drawing to relate to. I figured the weakest spring went on outside since that was the weakest way to push the handle. The next was to the inside and the heaviest springs were fore and aft.

It seemed to work the last time I did one. Also I've never had those things pop out on me. Usually I've had to use plier and a rag to pull the spools from the bores.


I thought the same thing about the springs John C. This was the left joystick, the strongest springs were fore and aft as you noted, stick extend/retract, which is the motion your arm has the most strength. Next lighter spring is swing right, which is a motion your arm still has some strength. The weakest spring, much weaker, was swing left, which motion your arm has the least strength. Seems there's some ergonomic design with these type configurations.

I've done this repair on the Hitatchi valves on 100's and 120's, same thing as you described, have to pluck the piston guides out, and setting them back isn't much of a chore either. This valve...it had some SPRING to it, took a good bit of hold down pressure to hold the stiff springs while fitting the retainer wire.



Atco, this forum wouldn't be the same without you!

Merry Christmas everyone


Merry Christmas to you as well watglen. :)

Wouldn't be the same? Bah ha ha haha
Hey, we got ourselves a "Shop" section on the forum for Christmas, so I'm gonna post some shop stuff here. ;)
 

coalrulz

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Good Question
I have rebuilt pilot controllers for deere and hitachi. I would always order new Brass piston guides and piston (as an assembly) and install. I agree with Atco, better to remove pilot controller from machine then repair.
 

BLconst

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Atco, I guess i broke the #1 rule and lost track of which spring goes where. i have 2 different types of spings for inside the plungers and 2 different ones for outside the plungers.IMG00037-20110124-1738.jpg
 

willie59

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Oh my BLconst, that doesn't look good. Unless you have very good parts diagrams, it's difficult to determine exactly where the components go, and they have to go in the correct orientation. What machine is it on? We'll do what we can to help you re-assemble it, but it's difficult for us on this end.

One thing you can do, if all other plans fail, is to take the opposite side joystick off and very carefully take it apart, probably needs seals anyway. The other joystick should be assembled in the same manner, just the opposite right hand/left hand orientation.
 

BLconst

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Its a cat 287b. drive stick (left). See if this pic clears it up. the large springs #6, i know where those go. My confusion is the little ones. Thank you for any help. I can take apart the right hand stick, but will it be the same since its a skid steer not an excavator?

scan0004.jpg
 

willie59

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Lee-online might be able to help you out with that one BLconst, he works at a Cat house. :D
 

BLconst

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Cat 287b left drive joystick.
trying to figure out if the tight spring goes with the loose spring or the loose with tight.option 1.jpg

or the tight with tightoption 2.jpg

and which one is forward/reverse and which pair is left right
 

willie59

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Yes sir, the large spring #6 are all the same.


Well, I'll take a wag at it, but keep in mind, it's only a best guess. The stiff springs pair up, and the weak springs pair up. The two stiff spring sets go in the for and aft motion, the two weak spring sets go in the left/right motion of joystick handle.
 

stumpjumper83

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I don't supose one could disassemble the opposite side and see how that side is paired up? Not to boubt atco's wisdom and experience, but.. I believe in a dozer the lighter springs are fore and aft, and the stif are in the side to side motions to help keep you driving in a straight line.
 

willie59

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I don't supose one could disassemble the opposite side and see how that side is paired up? Not to boubt atco's wisdom and experience, but.. I believe in a dozer the lighter springs are fore and aft, and the stif are in the side to side motions to help keep you driving in a straight line.

You could be right stumpjumper, I really can't say one way or the other, just doing like you and noodling through possibilities. :)

Consider this possibility though. When operating a dozer, you do make turns and changes in directions. With skid loaders, you are typically making constant turns and turnarounds. So it's possible that it would be oriented with the stiff springs for and aft, the direction your arm has the most strength, and the weak springs left and right, the direction your arm muscles are weaker to prevent arm fatigue from making constant turns.

Just a complete guess on my part. ;)
 

BLconst

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Well got 'er back together. Seemed to be okay. delay is gone but now machine has a left side weakness, goes forward and back fine, when i rotate full left or full right only the right track is turning. i swithched springs and plungers around and did not make a difference. Maybe ball resolver? maybe drive motor? I did notice that the ball resolver and the case for the plungers have updated, changed, part numbers. maybe time to dump the 1300 on new joystick complete, such a shame after a 500 sealkit!
 
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