An aggregate processing plant reported that a Volvo L150H wheel loader was overheating after just 20 minutes of operation. The hydraulic oil temperature would spike to 110°C, causing the implements to become sluggish and the steering to feel spongy. The machine had a brand-new hydraulic pump installed two weeks prior, and the oil cooler had just been cleaned.
The technician first checked the implement and steering pressures, which were within spec. However, the case drain flow from the pump was higher than expected, indicating internal leakage. But since the pump was new, the issue was suspected to be on the suction side.
The technician removed the hydraulic tank inspection cover. Inside the tank, a horizontal baffle plate is designed to separate the return oil from the suction line, allowing air bubbles to rise and debris to settle. The baffle plate had sheared all its spot welds and collapsed onto the bottom of the tank. This allowed the hot return oil to circulate directly into the suction strainer without cooling or de-aerating. The turbulence was creating a vortex that sucked air into the pump.
Furthermore, the suction hose (the hose running from the tank to the pump) was removed. The internal rubber liner had separated from the outer cover, collapsing inward. This "internal collapse" acted like a kink in a garden hose, starving the pump of fluid. The pump was forced to work harder to pull oil, generating immense friction heat and causing the cavitation that was damaging the new pump.
The repair involved welding the baffle plate back into position inside the tank and installing a new, reinforced suction hose with a higher collapse resistance rating. The hydraulic system was flushed to remove the varnish caused by the overheating. After reassembly, the oil temperature stabilized at a healthy 65°C, and the steering and implements operated smoothly.
