Descrição
A gear pump on a loader has a short list of jobs and a short list of ways to fail. What it does not have is a regulator, a control spool or any intelligence, which makes it the easiest component to diagnose and the easiest one to sell a substitute for. This page states what the catalogue supports and what it does not.
What Caterpillar lists
139-6084 appears in the Caterpillar catalogue as PUMP GP, and trade parts data describes the construction as an external gear pump. That is where the certainty ends. Cat’s title does not name the circuit the pump serves, and supplier listings variously describe it as a steering pump, a hydraulic gear pump or a power-steering oil pump for the 950G and 962G. We are not going to upgrade a supplier guess into a specification.
What this part is not
It is not a cooling fan pump. Fan drive pumps in the G-series loaders are piston units with a control assembly, and they carry different numbers. If you arrived here from a search for a fan pump, the loader pages you want are our 191-2942 fan pump for the G II machines and 254-5146 for the H series.
Applicability
CAT 938G, 950G and 962G wheel loaders and the IT38G and IT62G integrated toolcarriers, with the Cat 3126 and 3126B engine family. The Series II machines are a different parts set in several respects, so match the number on your old pump rather than the model badge on the door.
How a gear pump fails, and what it sounds like
Three mechanisms, and a workshop can separate them without special tools:
- Internal leakage across the gear tips and side plates. Flow falls as pressure rises. The symptom is a function that works when cold and slows when the oil is hot, because thin oil leaks more readily.
- Cavitation. A restricted suction line or a blocked strainer pulls a vacuum on the inlet, the pump noises, and the damage it does to itself looks like wear. If the old pump was growling, check the suction path before blaming the unit.
- Shaft seal failure. Almost always a back-pressure or mounting problem rather than a seal defect. Check that the drain and case lines were routed correctly when the pump was last removed.
Cleanliness is the common thread. The working target for piston components sharing the circuit is around ISO 4406 18/16/13 on Bosch Rexroth’s mobile hydraulics guidance, and a gear pump that has shed material will keep feeding the rest of the system for the next 500 hours unless the circuit is flushed and the element changed.
Fitting
Match shaft form and key, pilot diameter, flange bolt pattern, port thread sizes and the orientation of the ports against the removed pump. Prime before cranking. Change the return filter element and clear the suction strainer. Confirm rotation direction. Then check the pressure and flow against the machine’s specification rather than simply declaring the job finished, and log the readings so the next fault has a baseline.
Ordering
Send the number from your old pump and the machine serial prefix. Minimum order one piece, three to six month warranty on new aftermarket units as stated on your proforma invoice, wooden case, delivery 5 to 8 working days from payment subject to stock. Other Cat hydraulic components are under CAT hydraulic pump and the general bomba hidráulica para escavadeiras range, and our seal kit rebuild checklist explains what a proper hydraulic repair covers.
