Cummins/Onan — Cooling System Fill and Air Purge
Maintenance
From a Cummins/Onan service manual covering: 275 DFBF, 300 DFCB, 350 DFCC. Check it applies to your exact model before use.
Applies to: Cummins/Onan 275 DFBF, Cummins/Onan 300 DFCB, Cummins/Onan 350 DFCC, Cummins/Onan NT-855-G6 engine, Cummins/Onan NTA-855-G2 engine, Cummins/Onan NTA855-G3 engine
Before you start
- Do not open a radiator or heat exchanger pressure cap while the engine is running.
Procedure
- Remove the radiator pressure cap and monitor the coolant level on first start.
- Add coolant as trapped air is expelled and the level drops.
- Replace the pressure cap when the coolant level is stable.
Full service-parts list: Cummins/Onan 275 DFBF →, Cummins/Onan 350 DFCC →
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.