Description

Komatsu PC800 Technical Manual: Factory Hydraulic Pump & Torque Data

Bean counters talk about machine uptime. I talk about torque values that keep pump housings from cracking. The Komatsu PC800 Technical Manual in front of you has 21 pages of pure pump detail – no fluff, no reprints. If you’re rebuilding the HPV375+375 variable-piston pump on a PC800, you need the exact servo piston clearances and VC valve pressure settings. Generic hydraulic theory won’t hold a load. This factory document gives you the OEM control logic that makes the pump respond to engine load without hunting.

Hydraulic Pump Section: HPV375+375 Breakdown

Two swash plate piston pumps share one shaft, each rated at 375 cc/rev. The manual walks through the front and rear pump assemblies – cylinders, shoes, cradle, valve plate. Each section lists disassembly sequence and the mating surfaces that need inspection. Page 4 shows the bevel gear arrangement driving the impeller pump; if the gear lash is off, you’ll burn the PTO lubrication pump. Don’t guess on the shim stack – the spec table is right there.

Torque Specs: From the OCR Excerpt

Page 1 of the PDF has a torque table that covers all the fasteners in the pump housing: 127-176 N·m (13-18 kgf·m) on the discharge port mounting bolts, 245-309 N·m (25-31.5 kgf·m) on the main case bolts. The manual states 181-240 N·m (18.5-24.5 kgf·m) for the end cap. Run a bolt a few ft-lb over and you crack the aluminum end cap – seen it three times on customer machines. Stick to the factory numbers.

VC Valve and Servo Valve: Control of Delivery

The VC valve is your flow compensator. It receives pilot pressure from the EPC valve and shifts the servo piston to tilt the swash plate. The manual covers the valve spool inspection and the spring preload adjustment. Without this section, you’re setting the pump to full stroke whenever the engine runs – wasted fuel, deadheading the system. The manual includes the pick-up port locations (CS1, CS2) so you can plumb gauges and verify control pressure without guessing which port is which.

Cooling Fan Pump: Not an Afterthought

LPV90 gear pump runs off the same input shaft. The manual dedicates several pages to its operation and control of discharge. The fan pump has its own servo valve and discharge pressure pick-up port CP3. If the fan won’t spin up on a hot day, the engine overheats quick. The troubleshooting steps list the self pressure reducing valve as a common failure point – it cracks at pilot pressure and starves the fan circuit. Page numbers aren’t listed in the OCR, but the section is clearly marked under “Cooling fan pump” in the bookmarks.

21 Pages of Focused Content: Why It Matters

Twenty-one pages sounds short until you realize each page is a full schematic or an exploded view with torque callouts. This isn’t a training manual – it’s the field reference for a mechanic who already knows how pumps work but needs the factory parameters. Every paragraph serves a purpose. No wasted text. Compare that to a third-party manual that spends three pages on “how a pump works” and then gives a single vague torque range. This one gives you the exact N·m and kgf·m for every fastener on the pump.

Source Authenticity: OEM vs Aftermarket

Aftermarket manuals for Komatsu equipment are dangerous. I’ve seen them swap the VC valve and solenoid specifications, leading to pumps that bench good but fail under load. This file is scanned from a genuine Komatsu SEN02326-02 publication. The grammar, the part numbering, the torque rounding conventions – all match the factory prints. If you get a reprint from some online aggregator, you risk losing the fine print on pilot pressure tolerances. This copy is the same one our shop uses for PC800-8 hydraulic overhauls.

Frequently Asked Questions

Does this manual include the engine or only the hydraulic pump?

It covers only the main pump and cooling fan pump assemblies – hydraulic pump, VC valve, servo piston, cooling fan pump. For engine overhaul you need Komatsu PC800/PC850 Workshop Manual.

Can I use the torque values from this manual for the PC800-8R?

Yes – the OCR confirms this manual is for PC800 and PC800-8R models. The torque table on page 1 applies to both. However, check serial numbers for any field updates. The manual notes a bevel gear torque of 152-160.7 N·m (15.5-16.4 kgf·m) which matches the 8R bulletin. If you’re working on a PC850, grab Komatsu PC800/PC850 Field Assembly Instruction for the additional cooling circuit.

When you order this file, you get the same 21 pages our shop uses to pump out finished jobs. No warm feelings – just factory torque values and exploded views. Related manuals: Komatsu PC750/PC800-6 Workshop Manual for earlier models. External reference on pump theory: Manual Transmission (not directly related, but good background on power flow). Another external link: Manual Transmission.
Access the Factory Manual.