SUBJECT: Inspection of the Gear Pump for the Hoist on the 797 Off-Highway Trucks is Required

PROBLEM: Leaking oil from the two center sections on the 223-3749 gear pump has been found. The leaking is usually found in the very early hours of operation.

The oil will leak from a bolt hole. The leak is caused by the incorrect machining of the boss that contains the discharge port. The milled edge of the boss has excessive material that has been removed. The threaded holes for the mounting flange bolts are located on the milled surface of the boss. The machining error causes the threaded holes to be off location by approximately 6.35 mm (0.250 in). This will cause the threaded hole for the flange bolts to break into the pressure cavity inside of the body.

SOLUTION: Inspect the bodies of all of the gear pumps for the hoist that have serial numbers earlier than June, 2003. The serial number on the pump will show up as NF-nnnnn. The N stands for the year, 2003. The F stands for the month, June.

Threaded hole that broke through

Discharge port

Milled edge

The inspection can be performed by measuring the location of discharge port (2). The center of discharge port (2) should be 63.5 +/- 1.5 mm (2.50 +/- 0.06 in) from milled edge (3). The location of discharge port (2) on the defective parts will be 58.7 mm (2.31 in) from milled edge (3).

If a leak is found on a machine, remove the leaking pump from the machine. Replace the pump that is leaking with a new pump that has been manufactured after May, 2003. Return the leaking pump to Caterpillar Inc. ? Joliet for repair. If a leaking pump is found before installation on a machine, return the pump to Caterpillar Inc. ? Joliet for repair. For either case, the dealer will be required to submit a warranty claim in order to recover the cost of the pump.

The shipping address for the defective pumps is: