By Truck Parts & Service Staff
Each month in Diagnose This! we present a real-life service scenario with clues as to what the ultimate diagnosis was. If you think you know the answer, be the first to e-mail [email protected] with the correct response for free Truck Parts & Service merchandise. The answer will be revealed in a future issue of the magazine.
Vehicle: 2007 IH 4400 DT466
Key components: Hydraulic dump body, Allison automatic transmission
Scenario: This truck has a PTO-driven hydraulic pump with air-actuated controls for dump body operation. The dump body hydraulics consist of a “2 line” system where the pump oil supply is contained in the vented side of the hydraulic cylinder itself and there is no external reservoir or fluid return line. Since the vehicle was new, the pump has
suffered repeated premature leaks and failures.
Clues: The hydraulic oil was examined and found to be severely overheated but with no signs of abrasive wear. The PTO was tested and works correctly. The truck is programmed so that it cannot be driven while the PTO is engaged, and pump relief settings were verified correct. Pump RPM is programmed and confirmed correct. The hydraulic hoses are free of restriction and each new replacement pump corrected the condition for approximately one year.
