We have a dump truck with a Hyva cylinder in it. Tank is mounted behind the cab. Hydro keeps coming out through the fill cap/breather. About once or twice a week we need to top off the hydraulics. My assumption is that somehow air is getting sucked into the hydraulic system, pressurizing the tank and spitting it out the breather. We had a similar issue on a demo trailer cylinder that was sucking in air when it was coming down and it would air lock the valve on the tractor. With that, I'm assuming it may be the cylinder sucking in air. We've tightened and inspected all suction lines. What else could it be?
is the hyd. tank big enough for the cylinder or maybe the return line oil is getting directed toward the fill and as the bed is coming down because of weight or say the fluid is now hotter and returning faster and with more force gets directed toward fill by baffles or sides of tank
We have an identical sister truck that has no issues, so the tank should be the right size. With the oil getting directed to the incorrect spot, could that be the valve that's bypassing?
Is it a two hose hoist cylinder? If so, they need to be powered down.
I remember reading about a similar issue and seems like it was that the bed went down faster than the oil could flow, so it caused air to be pulled in through the cylinder seals.
Single hose
We ended up changing out the cylinder because it was starting to leak, but it still has the same issue. What else could be sucking in air? The shifter valve?
What wt. oil. Does the vent have the waded up scouring pad like stuff in it. Where the oil exits the cylinder could you make some kind of orfice fitting to just slow the flow down some
Cavitation, temperature, viscosity or pump issue.
We tested the pump pressure with a load on. Had about 1200 psi, should be around 2250psi. We changed the pump out and checked inside the tank. The suction line had a plastic tube that extended half way up the tank. Someone years ago must have put that in for some odd reason. We took that tube and now everything works as it should. Lesson learned: Check the tank suction line first.
Might be overfilled and warming up and growing