Cummins/Onan — Changing Coolant
Maintenance · Engine cooling system
From a Cummins/Onan operator's manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDKA, Cummins/Onan HDKAH
Before you start
- Hot coolant under pressure can spray and cause severe burns
Procedure
- Allow engine to cool before releasing pressure cap.
- Turn pressure cap slowly without pushing down until it catches.
- Remove pressure cap.
- Drain coolant by removing system drain cap.
- Optionally clean and flush system.
- Fill recovery tank with coolant mixture to COLD mark.
- Secure system drain cap.
- Fill cooling system through pressure cap/fill opening.
- Start and operate genset for few minutes.
- Shut down and add more coolant if necessary.
- Secure the pressure cap.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Capacity: 4.2 quarts (4 liters)
- Use ethylene or propylene glycol antifreeze
- Replace every 2 years
Full service-parts list: Cummins/Onan HDKA →, Cummins/Onan HDKAH →
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.