A quarry operation reported that a New Holland W270C wheel loader was becoming increasingly difficult to steer, requiring the operator to violently crank the steering wheel. Simultaneously, the bucket lift and tilt functions were agonizingly slow, especially when the engine was at low idle. The transmission and drive functions operated normally.
The technician first checked the main hydraulic pump pressure. At idle, the pump was only producing 150 psi, well below the 400 psi standby setting. When the steering wheel was turned, the pressure momentarily spiked to the relief setting of 2,500 psi but immediately dropped back down, causing the steering to catch and jerk.
Because both the steering and implement circuits were starved for flow, the technician suspected a restriction on the suction side of the pump. The hydraulic tank was drained, and the main suction filter was removed. The filter element had completely collapsed inward, resembling a crushed accordion. A thick layer of black, fibrous sludge had blinded the filter mesh.
The source of the sludge was traced to a disintegrating pilot filter element located upstream. The bypassing pilot filter had sent fibrous debris into the main tank, which immediately packed against the main suction screen.
However, the collapsed filter alone didn't explain why the system couldn't build standby pressure. The load-sensing shuttle valve, which routes pump flow to the steering or implements based on demand, was removed. The internal spool was heavily varnished and stuck in the "implement" position, preventing the steering circuit from receiving priority flow.
The repair involved flushing the hydraulic tank to remove all fibrous sludge, installing a new main suction filter, and replacing the pilot filter assembly. The load-sensing shuttle valve was disassembled, honed, and fitted with a new spool. After refilling with fresh ISO 46 hydraulic oil and bleeding the air from the system, the steering became effortless, and the implements operated at full speed, even at low engine RPM.
