Bobcat T66 Lift and Tilt Slow When Hot
Fault Codes & Symptoms
Lift and tilt functions are slow after the machine warms up. Related symptoms: - Hydraulic system seems to overheat more quickly than normal - A whining noise from the pump area may be heard when the system is hot and hydraulics are actuated The customer reports that the machine works fine for the first 30-60 minutes, but then the lift and tilt functions become very slow. Drive motors seem to have normal power.
Confirmed cause: The polymer seal ring on the hydrostatic pump control block for the charge pump circuit was found to be heat-hardened and cracked, causing a significant internal leak when the hydraulic oil was hot. Repair performed: Removed the hydrostatic pump assembly. Disassembled the pump sections to access and replace the failed control block seal ring. All related O-rings and seals were replaced at the same time. The pump was reassembled and reinstalled. Verification: After the repair, the machine was operated for over an hour under load. Charge pressure was monitored and remained stable and within the manufacturer's specification from cold start to full operating temperature. Lift and tilt function speeds were normal and consistent regardless of temperature. Technician notes: - This failure mode can be mistaken for a worn-out charge pump or a bad pressure regulator. The temperature-dependent nature of the symptom is the key clue. - Thoroughly cleaning the hydraulic oil cooler and ensuring the hydraulic fan is functioning correctly is critical to prevent premature seal failure due to overheating. - The old seal was extremely brittle. Care was needed during removal to prevent fragments from falling into the pump housing.