Control valve L555 skidsteer (2024)

Is your valve lever control or solenoid controlled?

If it is a spool valve, you are simply pushing or pulling a spool to connect lands and holes for the fluid to flow in a certain direction.

If it is a solenoid valve, you might have some wires crossed.

What do you mean by air lock?

If your pump IN port is flooded, the pump will push the fluid through all valves until it gets to the tank.

Any reverse flow is by lever or a switch or shorted wires.

The fluid flow follows the pathway of: pump to control valve (foot levers) to boom solenoid to boom cylinders to oil cooler to chain case. I was wondering if it might not be a loose connection because of the way it would work again if machine was jarred. Thankfully this was built before they got too much into electric and electronic controls. I do know of a wire going to boom solenoid and the seat safety switch (was bypassed before purchase). I will trace the wire for the solenoid and see what I can find and check coil for resistance. On the airlock, for some reason on the L555 if you refilled it with the strainer cap on it will trap air and the pump will not pick up fluid. Someone on the skidsteer forum told me to open the stainer and fill it through the strainer (faster) and would allow air to bleed out and not force fluid out of pump and lose prime is how I understood him. All I know is it worked.

This is the boom solenoid: Screenshot by Lightshot This is the control valve: Screenshot by Lightshot

I hope you can open them. In the mean time I am going to trace wires.

I am not sure air is the problem.

Air will expand and collapse due to heat and cooling, and bubbles might form from a suction leak and expand the fluid.

A more likely cause would be a blocked tank vent tube that will cause a vacuum, and might prevent the pump from picking up the prime.

Ivan49 said:

I have the same machine and mine did something similar. There is a rod going form the control valve to your foot pedal. Check the holes on the foot pedal end and see if the holes are badly egg shaped. If they are fix them. There is also an adjustment on that rod. With the boom down and the engine off work the foot pedal and see if it is moving the spool all the way in on you control valve. Hope this helps

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Good point. If linkage is worn enough at a picot point it could going over center which would move spool in opposite direction and not have full travel/stroke.