Cummins/Onan — Cooling System Fill and Venting
Maintenance
From a Cummins/Onan service manual covering: 200 DFP, 250 DFM, 275 DFM, 300 DFM. Check it applies to your exact model before use.
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Before you start
- Contact with hot coolant can result in severe burns. Allow cooling system to cool before releasing pressure and removing the radiator cap.
Procedure
- When the engine is first started, remove the pressure cap and monitor the coolant level.
- As trapped air is expelled from the system, the coolant level will drop; add additional coolant.
- Replace the pressure cap when the coolant level is stable.
Source: Cummins/Onan service 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.