PC128US-2 to PC158USLC-2: engines, fronts and service

PC128US-2 and PC138US-2: the engine change matters

The similar short-tail bodies hide different engines. The PC128US-2 brochure identifies an S4D102E, with mechanical governing and a larger displacement than the aftercooled SAA4D95LE-3 in the PC138US-2. Their power entries must retain their test standards.

The older sheet's SAE J1349 rating is net output; calling that number gross makes a comparison look more precise while changing what was measured.

Use the complete engine code when buying filters or diagnosing a fuel complaint. A discussion about an electronic PC130-8 controller does not establish what is fitted to a mechanically governed PC128US-2. The PC130, PC150LGP and PC158 entries remain separate in the comparison because their names describe different machines, not equipment packages for either short-tail excavator.

An offset front changes the trench you can reach

Komatsu's PC138US-2 literature covers a mono boom, a two-piece boom and an offset option. Offset equipment can place the bucket beside the machine, useful when the tracks cannot straddle the excavation. Its side reach is an additional capability, not extra straight-ahead digging depth.

Select the drawing for the installed front and then the arm column. Combining an offset measurement with the mono-boom maximum would describe a machine that is not in the brochure.

Counterweight clearance needs the same care. The standard rear envelope differs from the optional additional-weight arrangement shown for the articulated front. Measure the equipped rear before deciding that a machine can work entirely inside a marked corridor.

The cab's sliding door avoids a swinging door projecting into that corridor, but it does not cancel the counterweight's own clearance requirement.

The two hydraulic filter schedules are not interchangeable

For the PC128US-2, Komatsu describes a hydraulic filter element combining glass and graded paper media. The later PC138US-2 literature specifies a different, longer element interval. Those are different maintenance schedules.

An invoice saying only “Komatsu hydraulic service” leaves unanswered which element was fitted and which book the workshop followed. Match the parts receipt to the model and serial number, and distinguish the filter change from the separate oil-change interval.

The PC138US-2 cooling layout places the oil cooler, aftercooler and radiator alongside one another. The PC128US-2 material instead emphasizes its wave-fin radiator and dust screen. Inspect the actual cleaning access, including the back of the cores.

Dirt trapped behind an intact-looking screen can be missed in a photograph taken from outside the service door.