willie59
Administrator
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.