Cummins/Onan — Cooling System Flushing and Filling
Maintenance
From a Cummins/Onan owner's manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDKA, Cummins/Onan HDKAQ, Cummins/Onan HDKAR
Before you start
- Contact with hot coolant can cause severe burns.
- Never pour hot water into a cold engine or cold water into a hot engine.
- Coolant in a warm engine is under pressure; let engine cool before opening the radiator cap or drain cock.
Procedure
- Once a year, drain, flush and refill the cooling system with new coolant.
- Open the radiator coolant drain and the cylinder block drain.
- After cleaning, or before refilling, drain the system and fill with clean water.
- Run the genset for 10 minutes, then drain the system completely.
- Verify all drain cocks are closed and all hose clamps are secure.
- Remove the fill neck hose from the clamp, remove the pressure cap and slowly fill with coolant mixture.
- Start the engine, remove the pressure cap and monitor the coolant level; add coolant as trapped air is expelled.
- When the coolant level is stable, replace the pressure cap and add coolant to the recovery tank full-cold level.
Specs & values
- Cooling system capacity 1.25 gal (4.73 L)
- 50/50 ethylene glycol/water mixture provides freeze protection to -34°F (-37°C)
Full service-parts list: Cummins/Onan HDKA →, Cummins/Onan HDKAQ →, Cummins/Onan HDKAR →
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.