Pilot Pumps for Excavators: OEM-Quality Charge Pump Replacements for Komatsu, CAT, Hitachi & More

What Does a Pilot Pump Do on an Excavator?

On a hydraulic excavator, the operator does not directly move control valves with joystick force; instead, joystick movements generate small hydraulic pilot signals that travel through the pilot circuit to shift the spools inside the main control valve, which then directs high-pressure main pump flow to the commanded function. This two-stage system pilot circuit commanding the main circuit is what gives modern excavators their precise, responsive, and low-effort control feel.

The pilot pump is what keeps this entire pilot circuit pressurised. It runs continuously from engine start, maintaining a steady low-pressure supply typically between 40 and 60 bar to all pilot valve passages and solenoids. On most modern excavators, the pilot pump is a small gear-type or axial piston unit mounted in tandem with the main hydraulic pump on a shared drive shaft, meaning both units are driven simultaneously from the engine. When the pilot pump degrades or fails, the pilot pressure drops below the minimum threshold required to shift control valve spools, and machine response deteriorates or stops entirely.

Common Symptoms of Pilot Pump Failure

Because pilot pump failure mimics electrical and control system faults, correct identification is critical before ordering replacement parts. These are the most common indicators of pilot pump failure:

1. Complete loss of machine control — All joystick functions become unresponsive simultaneously. The engine runs normally, but no attachment or travel function operates.
2. Slow or delayed control response — Reduced pilot pressure causes sluggish valve spool actuation, resulting in delayed or weak function response across all circuits.
3. Machine functions only at high engine RPM — If the pilot pump is partially worn, it may only generate sufficient pressure at higher engine speeds, causing functions to drop out at idle.
4. Low pilot pressure warning or fault code — Machines equipped with pressure monitoring will generate a low pilot pressure alarm, directly indicating the pilot circuit as the source of the fault.
5. Intermittent control loss — Erratic pilot pump output caused by internal wear produces an inconsistent control response that comes and goes during operation.
6. Whining noise from the pump tandem assembly — Internal gear or piston wear within the pilot pump generates audible noise distinct from normal main pump operation.

If your excavator presents with any of these symptoms, test pilot circuit pressure before replacing joysticks, solenoids, or control valves. A simple pressure gauge test at the pilot circuit port will confirm whether the pump is the source of the fault.

Pilot Pump Models We Supply

Imara Engineering supplies pilot pump assemblies for a wide range of excavator models and production series. Our most commonly supplied models include:

• Komatsu — PC200-7, PC200-8, PC210-8, PC300-7, PC300-8, PC360-7, PC400-7, PC400-8
• Caterpillar (CAT) — 320C, 320D, 320D2, 323, 325C, 325D, 330C, 330D, 336D
• Hitachi — ZX200-3, ZX210-3, ZX300-3, ZX330-3, ZX450-3, EX200-5, EX300-5
• Volvo — EC210B, EC240B, EC290B, EC380, EC480
• Doosan — DX225LC, DX300LC, DX380LC, DX480
• Kobelco — SK200-8, SK300, SK350-8, SK480
• Hyundai — R210LC-9, R290LC-9, R380LC
• Case — CX210, CX300, CX350

Cannot find your model listed? Contact our parts team with your machine serial number and OEM part number, and we will confirm the correct pilot pump assembly for your specific unit immediately.

Tandem Pump Assemblies: Pilot Pump and Main Pump Combined

On the majority of modern excavators, the pilot pump is not a standalone unit; it is integrated into a tandem pump assembly alongside the main hydraulic pump and sometimes the gear pump, all mounted on a single drive shaft and housed within a common end-plate assembly. This configuration means:

• Replacing only the pilot pump — Possible on most tandem assemblies where the pilot pump section can be unbolted and replaced independently without disturbing the main pump section.
• Replacing the full tandem assembly — Recommended when the main pump has also failed or when the drive shaft, coupling, or shared components show signs of wear.
• Pilot pump as part of a three-pump tandem — Some larger excavators use a three-section tandem arrangement combining the main pump, second main pump section, and pilot pump in a single unit.

When ordering, specify whether you require the pilot pump section only or the complete tandem assembly. Our parts specialists will confirm the correct supply configuration for your machine model.

Pilot Pump vs Gear Pump: What Is the Difference?

The terms pilot pump and gear pump are sometimes used interchangeably in the field, which confuses when ordering replacement parts. Here is a clear distinction:

• Pilot pump refers specifically to the function of the pump that supplies the pilot control circuit. On many excavators, this pump is a small gear-type unit, which is why the terms overlap. However, on some higher-specification machines, the pilot pump is a small piston-type unit rather than a gear pump.
• A gear pump refers to a pump design external meshing gears to generate fluid flow. A gear pump can serve as a pilot pump, a charge pump, a cooling fan drive pump, or an auxiliary circuit pump, depending on where it is fitted in the hydraulic system.

When ordering from Imara Engineering, always specify your machine model and the circuit application pilot supply, and our team will confirm the exact pump type and specification required rather than relying on generic terminology.

Related Hydraulic Parts You May Need

Pilot pump replacement or failure diagnosis often connects to wider hydraulic circuit inspection. Consider sourcing these components alongside your pilot pump:

• Main Hydraulic Pumps — Inspect the main pump simultaneously when replacing the pilot pump in a tandem assembly
• Gear Pumps — Where the pilot function is served by a standalone gear-type pump
• Pump Seal Kits — For pilot pump rebuilds where internal components are serviceable
• Control Valves — Verify control valve spool condition if control response issues persist after pilot pump replacement
• Hydraulic Hoses & Pipes — Inspect pilot circuit hoses and fittings when diagnosing low pilot pressure faults