A swing motor that whines under load or an LS valve that won't hold its setting can idle a crew for days; this Komatsu PC88MR-6 shop manual PDF (Komatsu WEBM007200) is the 328-page factory answer for that hydraulic excavator. Disassembly and assembly fills more than a third of the book, working through the injection pump, engine head, radiator and A/C condenser, and the swing motor with its reduction gear. Hydraulic and electrical circuit diagrams close out the manual, and the structure and function chapter explains the power train, track frame and idler cushion, main pump, and control valve before you open any of them. Set the P1 general valve (boom, arm, bucket) to 265 bar, then confirm the engine holds 2080 ± 100 rpm with the pump at maximum pressure. Calibrating secondary valves from memory burns a whole shift. Bookmarked and text-searchable, the PDF is yours after one purchase, for as long as this machine runs.
What's Inside This Komatsu PC88MR-6 Manual
| System | Pages | Key Topics |
|---|---|---|
| Structure and Function | 27-132 | Power Train, Swing Machinery, Track Frame and Idler Cushion, Hydraulic Pump, Control Valve |
| Testing and Adjusting | 133-196 | Normal or Standard Technical Data, Checking the Exhaust Smoke Colour, Checking and Calibrating Pressure in the Secondary Valves, Checking and Adjusting the LS Valve |
| Disassembly and Assembly | 197-320 | Injection Pump, Engine Head, Engine Pumps, Complete Radiator and Air Conditioning Condenser, Swing Motor and Reduction Gear |
| Other | 321-328 | Hydraulic Circuit Diagram, Electrical Circuit Diagram |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Standard tightening torque for 6mm bolt (8.8 grade) | 0.96±0.1 kgm (9.5±1 Nm) | p. 12 |
| Standard tightening torque for 8mm bolt (8.8 grade) | 2.3±0.2 kgm (23±2 Nm) | p. 12 |
| Main relief valve pressure | 32 kg/cm2 | p. 53 |
| Engine speed with pump at max. pressure | 2080 ± 100 rpm | p. 136 |
| General valve P1 (boom – arm - bucket) pressure | 265 bar | p. 137 |
| Servocontrols feed valve pressure | 31.4 bar | p. 170 |
| Engine High Idling Speed | 2250 +100/-50 rpm | p. 135 |
| Engine Low Idling Speed | 1100 ± 50 rpm | p. 135 |
| Engine Oil Pressure (High Idling, SAE 30) | 3.5 – 5.5 kg/cm² | p. 135 |
| Engine Oil Pressure (Low Idling, SAE 30) | 1.8 kg/cm² | p. 135 |
| Fuel Injection Timing Advance | 5 ± 0.75 degrees | p. 135 |
| Swing Circle Grease Quantity | 5.5 l | p. 29 |
Komatsu PC88MR-6 Common Problems This Manual Covers
Komatsu PC88MR-6 engine speed drops too far when the hydraulic pump reaches maximum pressure under load
Measure engine high idle first and confirm 2250 rpm (+100/-50) on page 135. Then stall a circuit at relief and check engine speed with the pump at maximum pressure against 2080 ± 100 rpm on page 136. If you adjust the PC valve, torque its nut to 30-39 Nm per page 168.
Manual Section: Engine Troubleshooting p. 136Engine oil pressure reading low at high idle and low idle with SAE 30 oil
Connect a gauge and check oil pressure at both idle speeds. At high idle the spec is 3.5 to 5.5 kg/cm², and at low idle it is 1.8 kg/cm², both on page 135. If it reads low, confirm the idle speeds on the same page, then run the compression and blow-by checks in Engine Troubleshooting.
Manual Section: Engine Troubleshooting p. 135Load sensing (LS) valve out of adjustment with boom, arm and bucket cycle times running slow
Time boom, arm and bucket cycles against Work Equipment Speed Troubleshooting before touching anything. If they run slow, check the LS valve following page 167. One turn of the adjusting screw moves the setting 12.75 bar, so go in small steps. Torque the adjusting nut to 30-39 Nm and retest speeds.
Manual Section: LS Valve Adjustment p. 167Boom, arm and bucket circuit pressure reading low at the secondary valves
Check P1 pressure for boom, arm and bucket against 265 bar on page 137. If a circuit reads low, calibrate its secondary valve following page 164. One turn of the screw shifts pressure 125.5 bar, so use partial turns. Torque the lock nut and plug to 39-49 Nm, then recheck.
Manual Section: Secondary Valve Pressure Calibration p. 164Boom, arm, bucket or blade cylinders drifting down while holding a load
Run the drift tests on page 140 with a load of 620 kg in the bucket, one function at a time: boom, arm, bucket, boom swing, then blade. Pinpoint which circuit settles before you pull anything apart. After any repair that opens the circuit, bleed air from the cylinders per Air Bleeding Hydraulic Circuits before retesting.
Manual Section: Hydraulic Drift Analysis p. 140Machine tracking to one side with travel deviation out of spec on a straight run
Measure travel deviation following the Hydraulic System Troubleshooting checks. If one track lags, run the swivel joint leakage test to look for internal leakage. After opening the swivel joint or a travel motor, bleed air from the travel motors per the Air Bleeding Hydraulic Circuits procedure and recheck deviation.
Manual Section: Hydraulic System TroubleshootingFrequently Asked Questions
What are the hydraulic pressure settings for a Komatsu PC88MR-6?
The hydraulic pressure settings for the general valve P1 (boom-arm-bucket) are 265 bar (permissible 255-274.5 bar). The main valve P2 (boom swing-blade-swing) is set to 211 bar (permissible 201-221 bar). p. 137
How do I adjust the PC valve on a Komatsu PC88MR-6?
To adjust the PC valve, loosen the nut (2) and adjust the pump torque absorption with the screw (3). Turn the screw (3) while checking the engine speed monitor, as the PC valve is an eccentric design valve. Once adjusted, tighten the nut (2) to 30-39 Nm. p. 168
What is the standard valve clearance for the engine on the Komatsu PC88MR-6?
The standard valve clearance for the intake valve is 0.35 ± 0.02 mm, and for the dump (exhaust) valve, it is 0.50 ± 0.02 mm, measured at an ambient temperature of 20 °C. p. 135
What is the hydraulic oil tank capacity on the Komatsu PC88MR-6?
The first filling capacity for the hydraulic system is 110 liters, and the oil change quantity is 64 liters. p. 17
What is the tightening torque for the sprocket assembly bolts on the Komatsu PC88MR-6?
The sprocket assembly bolts require a two-stage tightening process: first to 80 Nm, and then to 230 ± 15 Nm, using a criss-cross torque sequence. p. 309
Is this Komatsu PC88MR-6 Shop Manual a digital download?
One searchable PDF covering 328 pages, delivered instantly. No disc, no shipping, no waiting on the post.
Can I print specific sections of this Komatsu PC88MR-6 Shop Manual?
Yes. Print the pages or sections you need for your own shop use. Any standard printer works.
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