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Part of the Case Repair Manuals.
This Case Corporation 688 Excavator Service Manual (OEM #8-66052) runs 769 pages deep on the Crawler Excavator platform, and it's built to answer questions your service history can't. You get full electrical schematics for the 24 Volt alternator and starter circuit, complete hydraulic schematics covering the high and low pressure pumps, and a dedicated troubleshooting section for the drive control and swing valve systems. Open to the engine chapter and you'll find real numbers: main bearing bolts torque to 129 lb ft (175 Nm), and the return filter needs replacing every 500 hours. No more pulling a torque wrench and guessing what Case actually specified back at the factory. Every chapter, from track rollers to the final drive transmission, is bookmarked so you can jump straight to the system giving you trouble. Pull it up on a tablet in the shop, search any spec by keyword, and get your 688 back on the job.
What's Inside This Case Corporation 688 Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 4-43 | Safety Rules, General Information and Torque Specifications, Detailed Engine Specifications, Maintenance and Lubrication |
| Engine | 44-277 | Engine Removal and Installation and Radiator Removal and Installation, Engine Accessories, Cylinder Head and Valve Train, Cylinder Block, Pistons, Rods, Camshaft, Main Bearings |
| Fuel System | 278-347 | Fuel Lines, Fuel Tank, And Engine Controls, Fuel System and Filters, Fuel Injection Pump and Drive Gear, Fuel Injectors |
| Electrical | 348-409 | Removal and Installation of Electrical Components, Electrical Specifications and Troubleshooting, Electrical Schematic, Batteries, Starter and Starter Solenoid, Volt Alternator |
| Track | 410-443 | Removal and Installation of Track Components, Troubleshooting, Track Chain and Shoes, Track Rollers, Idler, And Sprocket |
| Power Train | 444-513 | Removal and Installation of Power Train Components, Maintenance, Drive and Swing Motor, Final Drive Transmission, Swing Transmission |
| Hydraulics | 514-751 | Removal and Installation of Hydraulic Components, Maintenance and Service, Specifications and Troubleshooting, High Pressure Pump, Low Pressure Hydraulic Pump |
| Mounted Equipment | 752-765 | Boom, Arm, And Tool, Turntable Bearing and Related Parts |
| Schematics in Rear Pocket | 766-769 | Electrical Schematics, Location Schematics, Hydraulic Schematics |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Main Bearing Bolts Torque | 129 lb ft (175 Nm) (17.5 kgm) | p. 23 |
| Return Filter replacement interval | after every 500 hours of operation | p. 545 |
| No. 1 Compression 4T-390 Engine End Gap in 102.02 ID | 0.4 to 0.70 mm | p. 18 |
| Injection Pump Nut torque | 48 lb ft (65 Nm) (6.5 kgm) | p. 292 |
| Starter Torque for studs | 40 to 53 pound-inches (4.5 to 6.0 N m, 0.46 to 0.61 kg/m) | p. 381 |
| Engine Oil Pressure with Engine Warm at Rated Engine Speed | 42 to 54 PSI (290 to 372 kPa) (2.90 to 3.72 bar) | p. 13 |
| Main safety valve (in attachment control valve) pressure | 6185 to 6470 psi (42 646 to 44 511 kPa, 435 to 455 bar) | p. 551 |
| Engine Oil Capacity (with filter) | 11 Quarts | p. 13 |
| Fuel Tank Capacity | 58 U.S. gallons | p. 29 |
| Rated Engine Speed | 2040 to 2070 RPM | p. 13 |
| Valve Tappet Clearance (Exhaust) (Cold) | 0.508 mm | p. 13 |
| Cylinder Head Warpage (Maximum) | 0.20 mm | p. 18 |
Case Corporation 688 Common Problems This Manual Covers
Case 688 excavator engine overheats or stops under load, oil pressure gauge not in green zone
Stop the machine immediately and check the oil pressure gauge; normal warm running pressure at rated speed is 42 to 54 PSI (290 to 372 kPa) per the technical specifications on page 13. If pressure reads below that range, suspect turbocharger lubrication starvation from extended cranking without prime. Pull the turbo and inspect the center housing and shaft for scoring before you attempt a restart.
Manual Section: Technical Specifications p. 13Hydraulic system loses pressure or operates erratically during digging and lifting cycles
Shut down and relieve pressure before opening the tank. Pull the return filter from under the 3-bolt cover; replace it every 500 hours per the interval listed on page 545, sooner if the oil looks dark or metallic. Then check the main safety valve at the attachment control valve, spec'd at 6185 to 6470 PSI (435 to 455 bar) on page 551, and reset it if pressure has drifted low.
Manual Section: Hydraulics: Maintenance and Service p. 545Engine fires up then immediately stops right after cranking in cold weather
Confirm the fuel shutoff control is pushed all the way in and the turbocharger is primed before cranking in cold weather; cranking without a prime starves the turbo bearing and kills the engine on start. Work through the starting-problem checks for injection timing and shutoff linkage binding. If the injection pump was reseated, torque the pump nut to 48 lb ft (65 Nm) per page 292.
Manual Section: Diesel Fuel Injection System TroubleshootingStarter motor overheats or won't engage after cranking longer than 30 seconds
Never crank longer than 30 seconds at a stretch; let the starter cool for at least 2 minutes between attempts to keep it from overheating. If it still lags or won't engage, test the starter and solenoid circuit for excessive voltage drop under load. On reinstall, torque the starter mounting studs to 40 to 53 pound-inches (4.5 to 6.0 Nm) as specified on page 381.
Manual Section: Starting Circuit Troubleshooting p. 381Track slides off the drive sprocket repeatedly during travel over rough or uneven terrain
Check track tension first; a track riding up and off the sprocket usually points to a tensioner that has lost grease pressure or a worn recoil spring. Inspect the idler wheel and sprocket tooth profile for uneven wear that lets the chain walk. Reset tension to the interval called out in the maintenance schedule on page 39, then run the machine and recheck before returning it to work.
Manual Section: Track TroubleshootingFrequently Asked Questions
What are the torque specs for the main bolts on a Case 688 Excavator?
The manual provides specific torque specifications for critical engine components. For Cylinder Head Bolts, the torque is 93 lb ft (126 Nm, 12.6 kgm). For Main Bearing Bolts, the torque is 129 lb ft (175 Nm, 17.5 kgm). p. 22
How to reset the hydraulic system on a Case 688 Excavator?
While there isn't a specific "reset" procedure for error codes, the manual outlines steps for bleeding air and checking operation after service. For example, after installing the Main Hydraulic Pump, you should fill the hydraulic reservoir, start the engine at low idle for two minutes, and check for oil leakage. For the Hydraulic Swivel, after installation, start the engine at low idle, disengage the swing lock pin, and rotate the turntable 360 degrees in both directions to remove air and check for leaks. p. 518
What is the procedure to reset the engine on a Case 688 Excavator?
The manual describes a "Run-In Procedure For Rebuilt Engine" rather than a general reset. This involves disconnecting the electric shut-off wire, cranking the engine for 30 seconds until oil pressure is present, reconnecting the wire, and then running the engine at 1000 RPM minimum load for 5 minutes while checking for oil leaks, pressure, and coolant levels. p. 16
What are the replacement specifications for Return hydraulic filter?
Hydraulic filters should be changed after every 500 hours of operation or when the hydraulic filter warning lamp illuminates. The manual provides a procedure for removing and installing the return filter. p. 545
How will I receive this Case Corporation 688 Excavator Service Manual?
This is a 769-page searchable PDF ready for immediate download. Works on any device, so pull it up on your phone while you're under the hood. No shipping, no waiting.
Are there any print restrictions on this Case Corporation 688 Excavator manual?
No restrictions at all. Print individual pages, full chapters, or the entire manual. The PDF is completely unlocked.
Does this Case Corporation 688 Excavator manual have electrical diagrams?
Complete wiring diagrams are included, covering all electrical circuits, harness routing, and connector pinouts for the Case Corporation 688 Excavator.
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