obix
Member
Hello, I'm looking for some direction in resolving what I believe is a spool valve problem. Pretty sure this is a Husco valve, what I have matches what is in the Parts/Owners manuals for the Clark Michigan 75A Series I. I've included the parts diagram from the manual for the valve. At some point in the loaders life an external filter was added on the return side going back to the tank. I've been using AW-46 hydraulic oil.
Problem:
The boom lever periodically moves back on its own, from neutral position to lift, and the boom begins moving up. It does this with more force at higher rpm's. When the boom lever is held in the neutral position by hand everything seems to work normally, however if the lever is not physically held in the neutral position it will usually pop back to the lift position and the boom begin to rise again. There is no external leaking anywhere in the system that I can tell.
What I've Tried So Far:
I drained the system and removed the spool valve assembly. Removed the detent cover, detent spring and caps, then slid the spool out of the valve body. There is enough wear in the detent cover that the wear can be felt when running a finger inside, but does not seem extreme to me. The spool looks good and slides snugly in the valve body without any binding or catching. I did not remove the check valve from inside the spool (...yet). When in operation the detent can be felt moving through the positions ( lift / neutral / down / float ), it does feel on the weak side though. Also, I've noticed there is a lot of oil in the detent cap/cover #1, not sure if it's supposed to be there?
Pondering The Problem:
In the diagram this valve is represented by the parts #1-16. I suspect that either the spool is not centering when in neutral or possibly a weak spring #7 in the check valve.
I don't doubt that the detent spring #3 is on the weak side ( it's 60 years old... ) but not sure how this would account for the pressure on the spool -> boom lever that makes it want to pop into lift position, unless it's loose and there just happens to be enough play that it starts allowing fluid through...?
The seal #5 is bad leaking...?
Another thought, if it's alignment could the gasket #4 could be doubled up to set the detent further back, moving the spool away from the lift position and more into the neutral position...? (possibly just a band-aid over a bigger issue)
I may be barking up the wrong tree here, any thoughts or direction on how to proceed at this point would be greatly appreciated!
Problem:
The boom lever periodically moves back on its own, from neutral position to lift, and the boom begins moving up. It does this with more force at higher rpm's. When the boom lever is held in the neutral position by hand everything seems to work normally, however if the lever is not physically held in the neutral position it will usually pop back to the lift position and the boom begin to rise again. There is no external leaking anywhere in the system that I can tell.
What I've Tried So Far:
I drained the system and removed the spool valve assembly. Removed the detent cover, detent spring and caps, then slid the spool out of the valve body. There is enough wear in the detent cover that the wear can be felt when running a finger inside, but does not seem extreme to me. The spool looks good and slides snugly in the valve body without any binding or catching. I did not remove the check valve from inside the spool (...yet). When in operation the detent can be felt moving through the positions ( lift / neutral / down / float ), it does feel on the weak side though. Also, I've noticed there is a lot of oil in the detent cap/cover #1, not sure if it's supposed to be there?
Pondering The Problem:
In the diagram this valve is represented by the parts #1-16. I suspect that either the spool is not centering when in neutral or possibly a weak spring #7 in the check valve.
I don't doubt that the detent spring #3 is on the weak side ( it's 60 years old... ) but not sure how this would account for the pressure on the spool -> boom lever that makes it want to pop into lift position, unless it's loose and there just happens to be enough play that it starts allowing fluid through...?
The seal #5 is bad leaking...?
Another thought, if it's alignment could the gasket #4 could be doubled up to set the detent further back, moving the spool away from the lift position and more into the neutral position...? (possibly just a band-aid over a bigger issue)
I may be barking up the wrong tree here, any thoughts or direction on how to proceed at this point would be greatly appreciated!