A beverage distribution warehouse reported that a TCM FG30T9 3-ton LPG counterbalance forklift had developed a progressive cooling-system fault over a three-week period. The operator first noticed that the engine's operating temperature would climb noticeably above its normal range during extended loaded operation - particularly after 30 minutes of continuous load-and-carry cycles across the warehouse's concrete floor. The cab display would intermittently illuminate an engine overtemperature warning, and the operator reported that the truck's LPG fuel delivery would also begin to hesitate during the overheating events - the engine losing power and running roughly until the machine was allowed to cool. A faint grinding sound from the front of the engine was also noted during idle, and a small puddle of coolant was visible beneath the truck after each shift.
The technician first understood the FG30T9's cooling architecture and its interaction with the LPG fuel system. The engine's cooling system uses a centrifugal "Water Pump" mounted on the engine's front cover, driven by the engine's accessory belt, circulating coolant through the engine block, cylinder head, and radiator. The pump's shaft is supported on a sealed bearing assembly, and a mechanical "Shaft Seal" prevents coolant from leaking outward along the pump's shaft. The pump includes a "Weep Hole" - a small drainage port positioned below the shaft seal - that allows coolant leaking past a failing seal to escape externally rather than contaminating the pump's bearing. Critically, the engine's cooling system also supplies coolant to the "LPG Vaporizer-Regulator" - the device that uses engine coolant circulated through its internal passages to supply the heat required to vaporize liquid LPG before it reaches the engine's intake. When the cooling system overheats or its coolant flow is restricted, the vaporizer cannot receive adequate heat flow, and the LPG fuel system begins to deliver a lean, inconsistent fuel mixture - producing the hesitation and rough running the operator described during overheating events.
He verified the symptom by operating the truck under load and monitoring the engine's temperature gauge and the vaporizer's behavior during the overheating events. Within 30 minutes of loaded operation, the engine's temperature climbed into the warning range, and the engine began to hesitate and run roughly - confirming the fuel-delivery hesitation was linked to the cooling-system fault.
He inspected the radiator's external fins first. The radiator's fins were heavily packed with fine paper dust, plastic film fragments, and warehouse-floor debris - forming an insulating layer that restricted airflow through the radiator and reduced its heat-rejection capacity. He then inspected the water pump's weep hole. Fresh coolant residue was visible around the weep hole's exterior, and a droplet of coolant was actively forming at the port during idle - confirming the shaft seal had failed. He listened to the pump's bearing with a mechanic's stethoscope during idle. A faint grinding noise was clearly audible from the pump's bearing area - indicating the bearing had begun to degrade, likely from coolant contamination having migrated past the failed seal.
The root cause was traced to radiator fin blockage compounded by water pump seal and bearing degradation. The packed radiator fins had restricted airflow and elevated the engine's operating temperature. The water pump's shaft seal had failed, allowing coolant to leak past the seal and out through the weep hole, and the leaking coolant had migrated into the pump's bearing assembly - producing the grinding noise. The elevated engine temperature had reduced the coolant flow to the LPG vaporizer, causing the fuel-delivery hesitation the operator described during overheating events.
The repair involved pressure-washing the radiator's fins with low-pressure water (taking care not to damage the delicate aluminum fin surfaces), replacing the complete water pump with a new unit (the failed shaft seal and degraded bearing are not field-repairable), and replacing the accessory drive belt with a new belt (the old belt showed glazing from the degraded bearing's drag). The cooling system was flushed with a chemical flush solution to remove any degraded coolant and scale, and the system was refilled with fresh specified coolant to the correct level. The system was bled to remove trapped air, and the LPG vaporizer's coolant supply and return lines were inspected (both in good condition, with full coolant flow verified after the cooling system's restoration). After reassembly, a 60-minute loaded operational test showed the engine's operating temperature stable within its normal range, no coolant leakage from the weep hole, the grinding noise eliminated, and the LPG fuel delivery running smoothly throughout the test cycle with no hesitation. Radiator fin cleaning and water pump weep-hole inspection were added to the truck's 500-hour preventive maintenance checklist.
