Cummins/Onan CFP11E — Cooling System Drain, Flush and Refill
Maintenance · Cooling system / heat exchanger
For the Cummins/Onan CFP11E, from the Cummins/Onan operator's manual.
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Before you start
- Do not remove pressure/fill cap from a hot engine - wait until below 50 °C (120 °F)
- Coolant is toxic - avoid prolonged skin contact
Procedure
- Disconnect both batteries, negative cable first.
- Remove the coolant expansion tank pressure/fill cap.
- Disconnect the engine coolant heater power supply.
- Place a container holding at least 57 liters (15 gallons) under the coolant drain valve.
- Ensure coolant filter shut-off valves are OPEN.
- Open the drain petcock on the lower coolant tube and drain the coolant.
- Disconnect the engine heater coolant hose and drain the heater.
- Flush with clean fresh water or heavy-duty heat exchanger cleaner.
- Remove and replace the water coolant filter using a filter wrench.
- Reconnect the heater hose and close the drain petcock.
- Fill the coolant tanks with a 50% water / 50% ethylene-glycol or propylene-glycol antifreeze mixture.
- Check the pressure/fill cap condition and replace if worn or damaged.
- Reinstall heater wiring and battery cables (negative cable last).
- Operate the engine to 82 °C (180 °F) and check for leaks.
Tools required
- filter wrench Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 57 L (15 gal) minimum drain container
- 50% antifreeze concentration (40-60% range)
Source: Cummins/Onan operator'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.