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I'm dealing with hydraulic oil coming out of the tank breather on my 2015 8018. I've replaced the filters and oil, but it's still happening. It seems like the return line is always under pressure, does anyone know what might be causing this?
Constant pressure in the return line points to a bad restriction. Could be the bypass valve in the filter housing stuck shut, forcing all flow through the media and building up backpressure. Did you check if that valve moves freely when you swapped the filter? That's usually where we start when oil's pushing out the breather.
I didn't check the bypass valve when I changed the filter, I really didn't even think of that. I'll inspect it next. If it's stuck, would that explain constant return pressure?
I didn't check the bypass valve when I changed the filter, I really didn't even think of that. I'll inspect it next. If it's stuck, would that explain constant return pressure?
Yes, if a bypass valve, particularly one in the return line filter housing, is stuck open or partially open, it would definitely explain constant return pressure and potentially oil coming out of the breather.
Also, double-check that you've got the correct oil viscosity!
I want to add a clarification here for @Valeryon's benefit. The high return pressure would be caused by the bypass valve being stuck in the closed position, not open. A valve stuck open would create a path of lower resistance for the oil flow. Confirming the correct oil viscosity is also a crucial diagnostic step.
