Part of the Case Repair Manuals.
Need to rebuild the drive motor on your crawler excavator? This 927-page Case 688 service manual pdf (OEM #DON 8-88991) breaks down every component from the final drive transmission to the turntable bearing. You get complete hydraulic schematics detailing the swing control valve circuits and full electrical wiring diagrams for tracking down parasitic draws. Open up the engine section to find detailed troubleshooting charts and page after page of step-by-step teardown procedures. Verify the No. 1 compression ring end gap sits between 0.25 and 0.55 mm, then torque the boom cylinder piston to exactly 400 Nm. Guessing clearances leads to blown engines and wasted weekends. Grab this bookmarked file, pull it up on your shop tablet, and start turning wrenches.
What's Inside This Case 688 Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 6-35 | Sectional Index, Safety, General Information and Torque Specifications (Standard Torque Data for Nuts and Bolts, Torque Data for Hydraulic Fittings) |
| Engine | 36-263 | Cylinder Head, Valve Train, Cylinder Block, Pistons, Crankshaft, Camshaft |
| Fuel System | 264-327 | Fuel Filters, Fuel Injectors, Fuel Injection Pump, Fuel Shutoff Solenoid, Primer Pump, Injection Pump Timing |
| Electrical | 328-432 | Alternator, Battery, Starter Motor, Electrical Schematics, Troubleshooting, Printed Circuit Board |
| Track | 433-458 | Front Idler, Track Roller, Sprocket, Spring |
| Power Train | 459-530 | Drive Motor, Final Drive Transmission, Swing Motor, Swing Reduction Gears, Brakes |
| Hydraulics | 531-869 | Hydraulic Troubleshooting, High Pressure Pump, Attachment Valve Bank, Drive Control Valve, Swing Control Valve, Hydraulic Oil Tank |
| Mounted Equipment | 870-927 | Upperstructure, Turntable Bearing, Boom, Dipper, Bucket, Cab |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Standard Torque Data for Nuts and Bolts (10 mm, Grade 8.8) | 44 Nm / 32 lb-ft | p. 11 |
| Boom Cylinder Piston to Piston Rod Torque | 400 Nm / 295 lb ft | p. 838 |
| Piston Rings No. 1 Compression End Gap in 102.02 ID Cylinder | 0.25 to 0.55 mm | p. 117 |
| Piston Rings No. 1 Compression Side Clearance | 0.075 to 0.120 mm | p. 117 |
| Radiator Cap Pressure | 1.03 Bar / 15 psi | p. 55 |
| Lower Radiator Mounting Bolts Torque | 44 Nm / 32.5 lb ft | p. 55 |
| Pilot Circuit (servo-asistance) Operating Pressure | 33 to 36 Bar / 478 to 522 psi | p. 535 |
| Boom Flow Setting (Flowmeter) | 148 to 155 l/min / 39.1 to 40.9 US gal/min | p. 544 |
| Thermostat Fully Open Temperature | 94°C / 201°F | p. 22 |
| Engine Oil Capacity (with filter change) | 10.5 litres | p. 17 |
| Fuel Tank Capacity | 247 litres | p. 17 |
| Total Hydraulic System Capacity | 155 litres | p. 17 |
Case 688 Common Problems This Manual Covers
Case 688 hydraulic system pressure loss and sluggish boom movement during heavy digging tasks p. 544
Test the boom flow setting using a flowmeter. Adjust the system so the flow reads between 148 and 155 l/min as specified on page 544. Check the pilot circuit operating pressure to ensure it holds steady between 33 to 36 Bar.
Manual Section: HydraulicsEngine overheating under heavy load with reduced power output and active ENG-02 fault code p. 22
Inspect the cooling system radiator for leaks or internal clogging. Replace the radiator cap if it cannot hold 1.03 Bar of pressure. Verify the thermostat is fully open at 94°C as shown on page 22. Torque lower radiator mounting bolts to 44 Nm.
Manual Section: EngineLower piston wall wear and excessive piston ring groove wear after operating in dusty conditions p. 117
Inspect for dusting failure allowing contaminants into the engine lubrication system. Measure the No. 1 compression ring end gap; replace rings if the gap falls outside 0.25 to 0.55 mm. Verify ring side clearance is within 0.075 to 0.120 mm according to page 117.
Manual Section: EngineEngine surges at idle or produces fog-like white exhaust with noticeable low power output p. 24
Drain and clean the fuel lines to remove trapped air or water. Test the fuel injectors for proper pop-off action. Replace any injector that fails to meet the strict opening pressure specification of 231 to 253 Bar listed on page 24.
Manual Section: Fuel SystemFrequently Asked Questions
Torque specs for boom bolts?
The manual provides general torque data for nuts and bolts based on size and grade on page 11. For specific boom components, the diagram on page 894 shows '9. SCREW' and '10. LOCK NUT' for boom cylinder mounting, but no specific torque values are listed for these bolts in the surrounding text or specifications.
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