Line Leak Below Valve Drains Tank ????

[Gordon Gould]

This is an off the wall question but I am just trying to figure out how this happens to get a better under standing. I have a small dozer and when I get a hydraulic leak in a line or hose down stream from the control valve it will drain the tank. Has happened 3 times over the years. Some times the tank drains to the return line level and other times the suction line. My tractor does not do this but the tank is lower. The dozer valves are more complicated with load checks and anti cavitation valves that I am not clear on but looking a the diagrams I can't see a leak path to the tank. So what is happening.

It is disconcerting when you crack a line and don't know it then when you come back a couple weeks later there is oil on the ground and the tank 2/3 empty.

gg

 

[kthompson]

Don't have a dozier but do excavator and never had this to happen with it. Wondered about the vent cap but hard to believe the vent is it. Wonder if there is suppose to be a check valve in the return line and it is stuck or has failed or missing.

 

[oldnslo]

Is the reservoir higher than the valve stack? If yes it is possible that a line cracked could allow oil to be siphoned across the anti-cav checks and drain the reservoir. The anti-cav check have very low cracking pressure are intended to draw oil from the return line into the system to prevent cavitation.

 

[Gordon Gould]

Thank you. Yes, the oil level in a properly full tank is well above the valve stack. Also the tank breather is designed so that the tank builds up and holds pressure. Enough that you can hear it escape when you open the 4" cap. That wouldn't last long with oil leakage but it might help get a siphon action going ???

gg