Cummins/Onan — Draining the Cooling System
Maintenance
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Procedure
- Open all drains and hose connections where water could be trapped.
- Remove radiator petcock at lower right front corner.
- Remove engine block drain plug at left front near water pump.
- Remove water pump drain plug under cover or loosen the cover.
- If an optional water jacket tank heater is used, drain and flush it also.
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.