Cummins/Onan — Cooling system drain and flush (heat exchanger)

Maintenance

From a Cummins/Onan owner's manual covering: CFP-015, CFP11E, CFP15E, CFP23E, CFP30E, CFP50, CFP59, CFP5E, CFP60E, CFP7E, CFP83, CFP83-F10…. Check it applies to your exact model before use.

Applies to: Cummins/Onan CFP23E, Cummins/Onan CFP83-F10, Cummins/Onan CFP83 engine

Procedure

1. Disconnect both batteries at their terminals; remove the negative (-) cable first.
2. Press down, unscrew, and remove the coolant expansion tank pressure/fill cap.
3. Disconnect the engine coolant heater power supply before draining.
4. Place a container holding at least 57 liters (15 gallons) under the coolant drain valve.
5. Ensure the coolant filter shut-off valves are OPEN.
6. Open the drain petcock on the lower coolant tube and drain the coolant.
7. Move the container under the engine coolant heater, disconnect a heater coolant hose, and drain the heater.
8. Flush with clean fresh water or heavy-duty heat exchanger cleaner.
9. Remove the water coolant filter with a filter wrench, clean the housing, coat the new gasket with 15W-40 oil, and install; tighten an additional 1/4 turn.
10. Reconnect the heater coolant hose and close the drain petcock.
11. Fill the coolant tanks with 50% water and 50% ethylene-glycol or propylene-glycol antifreeze.
12. Check the pressure/fill cap condition and re-install.
13. Re-install the heater wiring.
14. Reinstall the battery cables; attach the negative (-) battery cable last.
15. Operate the engine until it reaches 82 C (180 F) and check for coolant leaks.

Full service-parts list: Cummins/Onan CFP23E →, Cummins/Onan CFP83-F10 →

Source: Cummins/Onan owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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