My 428F backhoe's hydraulic system is expelling oil through the filler cap, and the oil is bubbling vigorously in the reservoir. What might be causing this issue?
It seems like your 428F backhoe's hydraulic system might have a pressure issue. The oil bubbling in the reservoir and expelling through the filler cap could be due to excessive pressure. This might be caused by a faulty pressure relief valve or a blockage in the system. I would recommend checking these components.