D5G WGBO2007 Owned dozer about ten years. Never had to add oil between changes. Today it was low. After running a couple of hours I noticed hydraulic oil site glass was full. Opened cap and hydraulic tank is almost full to the top. Other than the pump on side of engine. Are there any other pumps or sources for the engine oil to escape to the hydraulic tank.
Is the oil in the tank in any way dark.? If it was contaminated with engine oil it ought to be dark and opaque instead of bright & transparent. There is a breaker/relief valve #2 on the hydraulic tank. Is it clean and functioning.? If it is not all sorts of weird things could happen to the fluid level.
I don't recall if your model is a hystat transmission or a power shift. Hydraulic oils have a terrific expansion factor involved when it warms up. If you added oil and now the level is over the sight glass, that is pretty normal. Have you noticed any of the other levels being low?
It's a Hystat.
The oil is dark now. I couldn’t tell if it smelled like engine oil or not. The cap had pressure on it when I loosened it. Will definitely check the valve you highlighted. It is a hydrostatic. I have not added hydraulic oil in a month or so. Since the last time I blew a hydraulic line. Yes I have noticed the level varies a lot. But yesterday it was almost to the bottom of the fill neck.
That valve works in both directions. First as a check valve to let air into the tank when the level drops. So if you remove it and suck on the threaded end (after cleaning it of course) you should be able to suck air through it quite easily. The vacuum setting is 0.5psi. Second it functions as a pressure relief valve and should open at 15psi when pressurized from the threaded end.