Caterpillar C12 Generator Set

⚠ Replace belts that are worn or damaged.

⚠ For multiple drive belts, replace the belts in matched sets.

1. Loosen mounting bolts (2) and adjusting bolt (1).
2. Move the alternator in order to increase or decrease the belt tension.
3. Tighten adjusting bolt (1). Tighten mounting bolts (2).

⚠ Fuel leaked or spilled onto hot surfaces or electrical components can cause a fire.

⚠ Never wire brush or scrape a fuel injection nozzle.

Tools: 8S-2245 Injection Cleaning Tool Group

1. Start the engine.
2. Loosen each fuel line nut one at a time at the fuel injection pump. Tighten each nut before loosening the next.
3. A defective nozzle may be identified when the exhaust smoke is eliminated and engine performance is not affected.
4. Remove the suspected defective nozzle and install a new nozzle to confirm.

⚠ Do not use a high concentration of caustic cleaner to clean the core.

⚠ Personal injury can result from air pressure. Wear a protective face shield and protective clothing.

Tools: 1U-5490 Hydrosolv 4165, 174-6854 Hydrosolv 100

1. Remove the core. Refer to the Service Manual for the procedure.
2. Turn the aftercooler core upside-down in order to remove debris.
3. Back flush the core with cleaner. Use Hydrosolv liquid cleaner.
4. Steam clean the core in order to remove any residue. Flush the fins.
5. Wash the core with hot, soapy water. Rinse thoroughly with clean water.
6. Dry the core with compressed air in the reverse direction of normal flow.
7. Inspect the core for cleanliness. Pressure test the core. Repair if necessary.
8. Install the core. Refer to the Service Manual for the procedure.

⚠ Batteries give off combustible gases which can explode. Ensure proper ventilation and prevent arcs and sparks.

⚠ Remove the battery cover before any servicing is attempted.

1. Turn the key start switch to the OFF position. Remove the key and all electrical loads.
2. Turn OFF the battery charger. Disconnect the charger.
3. Disconnect the NEGATIVE "-" cable from the NEGATIVE "-" battery terminal.
4. Disconnect the POSITIVE "+" cable from the POSITIVE "+" battery terminal.
5. Remove the used battery.
6. Install the new battery.
7. Connect the cable from the starting motor to the POSITIVE "+" terminal.
8. Connect the cable from the ground plane to the NEGATIVE "-" terminal.

⚠ All lead-acid batteries contain sulfuric acid which can burn skin and clothing. Wear a face shield and protective clothing.

Tools: 1U-7298 Coolant/Battery Tester (C), 1U-7297 Coolant/Battery Tester (F), 5N-5561 Silicone Lubricant

1. Remove the filler caps. Maintain the electrolyte level to the "FULL" mark on the battery.
2. Check the condition of the electrolyte with a Coolant/Battery Tester.
3. Keep the batteries clean; clean the case with baking soda and water or ammonia and water.
4. Clean terminals and cable clamps with fine sandpaper; coat with silicone lubricant, petroleum jelly or MPGM grease.

⚠ Removing the battery cables or batteries with the cover in place may cause a battery explosion resulting in personal injury.

1. Turn the start switch to the OFF position. Turn the ignition switch (if equipped) OFF and remove the key.
2. Disconnect the negative battery terminal at the battery that goes to the start switch.
3. Tape the leads in order to help prevent accidental starting.
4. Proceed with necessary system repairs. Reverse the steps in order to reconnect all of the cables.

⚠ Use only cooling system cleaners that are approved for Caterpillar engines.

⚠ Pressurized System: Hot coolant can cause serious burns. Loosen the pressure cap slowly.

Tools: 9S-8140 Pressurizing Pump

1. Stop the engine and allow the engine to cool. Loosen the filler cap slowly to relieve pressure. Remove the cap.
2. Open the cooling system drain valve (if equipped) or remove a drain plug. Allow the coolant to drain.
3. Flush the cooling system with clean water in order to remove any debris.
4. Close the drain valve. Clean and install the drain plugs.
5. Fill with clean water and Caterpillar Fast Acting Cooling System Cleaner. Install the filler cap.
6. Run the engine at low idle for a minimum of 30 minutes. Coolant temperature at least 82 C (180 F).
7. Stop the engine, cool, drain, and flush with clean water until all signs of cleaning agent are gone.
8. Close the drain valve. Clean and install the drain plugs.
9. Fill the cooling system with coolant/antifreeze. Do not install the filler cap.
10. Run the engine at low idle. Increase rpm to 1500 rpm and run high idle for one minute. Stop the engine.
11. Check the coolant level; maintain within 13 mm (0.5 inch) below the bottom of the filler pipe.
12. Clean the filler cap, inspect the gasket. Replace cap if damaged; otherwise pressure test with a 9S-8140 Pressurizing Pump.
13. Start the engine. Inspect the cooling system for leaks and for proper operating temperature.

⚠ Pressurized System: Hot coolant can cause serious burns. Loosen the pressure cap slowly.

Tools: 9S-8140 Pressurizing Pump

1. Stop the engine and allow the engine to cool. Loosen the filler cap slowly to relieve pressure. Remove the cap.
2. Open the drain valve (if equipped) or remove the cooling system drain plugs. Allow the coolant to drain.
3. Flush the cooling system with clean water in order to remove any debris.
4. Close the drain valve. Clean and install the drain plugs.
5. Fill the cooling system with clean water. Install the cooling system filler cap.
6. Start and run the engine at low idle until the temperature reaches 49 to 66 C (120 to 150 F).
7. Stop the engine, cool, drain, and flush the cooling system with clean water.
8. Close the drain valve. Clean and install the drain plugs.
9. Fill the cooling system with Extended Life Coolant (ELC). Do not install the filler cap.
10. Run the engine at low idle, increase to high idle for one minute to purge air. Stop the engine.
11. Check the coolant level within 13 mm (0.5 inch) below the bottom of the filler pipe.
12. Clean the filler cap, inspect the gasket, and pressure test with a 9S-8140 Pressurizing Pump.
13. Start the engine. Inspect the cooling system for leaks and for proper operating temperature.

1. Loosen the filler cap slowly in order to relieve pressure. Remove the filler cap.
2. It may be necessary to drain enough coolant in order to add the Extender.
3. Add Extender according to the requirements for your engine's cooling system capacity.
4. Clean the filler cap. Inspect the gaskets. Replace the cap if gaskets are damaged. Install the cap.

⚠ Pressurized System: Hot coolant can cause serious burns. Check the level when the engine is stopped and cool.

1. Remove the cooling system filler cap slowly in order to relieve pressure.
2. Maintain the coolant level within 13 mm (0.5 inch) of the bottom of the filler pipe, or to the proper sight glass level.
3. Clean the filler cap and check the condition of the filler cap gaskets. Replace if damaged.
4. Inspect the cooling system for leaks.

⚠ Cooling system coolant additive contains alkali. Avoid contact with skin and eyes.

⚠ Never use both liquid supplemental coolant additive and the spin-on element at the same time.

Tools: 8T-5296 Coolant Conditioner Test Kit, 4C-9301 Coolant Conditioner Test Kit

1. Slowly loosen the filler cap in order to relieve pressure. Remove the filler cap.
2. If necessary, drain some coolant in order to allow space for the extra SCA.
3. Add the proper amount of SCA.
4. Clean the filler cap. Inspect the gaskets. Replace if damaged. Install the filler cap.

1. Inspect the wiring harness for good connections.
2. Tighten the cylinder head grounding stud at every oil change.
3. Clean the cylinder head grounding stud and the terminals with a clean cloth.
4. If the connections are corroded, clean with a solution of baking soda and water.
5. Keep the stud and strap clean and coated with MPGM grease or petroleum jelly.