s160 hydraulic schematic.

[vhehn]

does any one have a picture of the control valve hydraulic schematic for a 2011 s160? manual controls. serial a3l336286. I am trying to diagnose a bucket lift cylinder drift problem. the bucket has a pretty fast drop like 5 min top to ground. you can hear a hiss like oil leaking through an orifice when the buck is sinking. I have already resealed the spools and inspected the load check valves. I have also plugged off the emergency lowering valve. I suspect there is some other check valve leaking in the control valve.

 

[Tazza]

Pretty sure this valve has electric lock outs for the hydraulics, but what happens if you are in the seat, whut the engine off, and turn the key on, press the push to operate button and move the pedal backwards. Does it stop the bucket drift? If so, i suspect an issue with the centering spring.
Have you re-sealed the cylinders?
Another possibility was the centering spring, if it is broken or weakened somehow, it could not be holding the spool in neutral.
In the lift section in the valve you have load checks (chich you said you have checked already), but you also have a relief valve, is it possible there is something stuck in there? I'm not sure if there is one in the tilt section though.

 

[vhehn]

Pretty sure this valve has electric lock outs for the hydraulics, but what happens if you are in the seat, whut the engine off, and turn the key on, press the push to operate button and move the pedal backwards. Does it stop the bucket drift? If so, i suspect an issue with the centering spring.
Have you re-sealed the cylinders?
Another possibility was the centering spring, if it is broken or weakened somehow, it could not be holding the spool in neutral.
In the lift section in the valve you have load checks (chich you said you have checked already), but you also have a relief valve, is it possible there is something stuck in there? I'm not sure if there is one in the tilt section though.

I tried your test with the key on but engine off. it has no effect. I have not rebuilt the cylinders yet. everything I read says that a dual action cylinder cant cause drift if the system has load check valves. is that incorrect? second reason is I can hear an oil leak sound inside/near the control valve when I raise the bucket and shut the engine off. that's why i need a schematic so I can determine the location of other valves that might be leaking.

 

[Tazza]

I tried your test with the key on but engine off. it has no effect. I have not rebuilt the cylinders yet. everything I read says that a dual action cylinder cant cause drift if the system has load check valves. is that incorrect? second reason is I can hear an oil leak sound inside/near the control valve when I raise the bucket and shut the engine off. that's why i need a schematic so I can determine the location of other valves that might be leaking.

I never did ask, is it indeed the lift cylinders that are leaking down? and not the tilt?
In theory a double acting cylinder will not move if the piston seal is bad, but in practice, it still does. Load checks are meant to prevent the cylinder from falling slightly before extension/retraction i thought, i could be wrong though. My understanding is that they are there to make operation smoother, not to hold all the fluid back, that is the job of the spool.
As you can hear noise, it does sound like it must be something else, personally, i'd start with the relief valve.
It will be screwed into the rear of the valve body, facing the engine. It will be inline with the lift segment of the control block. The one on the front should be your main relief valve, this is only under pressure when the engine is running.
Hopefully that is the cause of the problem, something stuck in it.
It is possible, rare but possible, that there is an intenal crack in the control block too. I know of at least one member that had issues that turned out to be a crack. His was different though, he would lift and it would affect the tilt as well, so fluid was passing between sections.

 

[vhehn]

I never did ask, is it indeed the lift cylinders that are leaking down? and not the tilt?
In theory a double acting cylinder will not move if the piston seal is bad, but in practice, it still does. Load checks are meant to prevent the cylinder from falling slightly before extension/retraction i thought, i could be wrong though. My understanding is that they are there to make operation smoother, not to hold all the fluid back, that is the job of the spool.
As you can hear noise, it does sound like it must be something else, personally, i'd start with the relief valve.
It will be screwed into the rear of the valve body, facing the engine. It will be inline with the lift segment of the control block. The one on the front should be your main relief valve, this is only under pressure when the engine is running.
Hopefully that is the cause of the problem, something stuck in it.
It is possible, rare but possible, that there is an intenal crack in the control block too. I know of at least one member that had issues that turned out to be a crack. His was different though, he would lift and it would affect the tilt as well, so fluid was passing between sections.

yes lift only. I too think its a valve in the control box.i just need to figure out which one. I guess I will pull and inspect them all one at a time until I find it.