Cummins/Onan — Drain and Flush Cooling System
Maintenance
From a Cummins/Onan owner's manual covering: 6CTA8.3, CFP83-F10, CFP83-F20, CFP83-F30, CFP83-F40. Check it applies to your exact model before use.
Applies to: Cummins/Onan 6CTA8.3, Cummins/Onan CFP83-F10, Cummins/Onan CFP83-F20, Cummins/Onan CFP83-F30, Cummins/Onan CFP83-F40, Cummins/Onan 6CTA8.3G2 engine, Cummins/Onan 6CTAA8.3G3 engine
Before you start
- Never use water alone for coolant.
- Wait until the temperature is below 50°C [120°F] before removing the coolant system pressure cap.
Procedure
- Drain the cooling system by opening the drain valve on the heat exchanger and removing the plug in the bottom of the water inlet.
- Check for damaged hoses and loose or damaged hose clamps; replace as required.
- Fill the system with a mixture of sodium carbonate and water (0.5 kg per 23 liters of water).
- Operate the engine for 5 minutes with the coolant temperature above 82°C [180°F], then shut off and drain.
- Fill the cooling system with clean water and operate for 5 minutes above 82°C [180°F]; drain.
- Repeat flushing until the drained water is clean.
- Fill with a mixture of 50-percent water and 50-percent ethylene glycol antifreeze.
Tools required
- Drain pan with a capacity of 20 liters [5 gal] Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Use 0.5 kg [1.0 lb] of sodium carbonate for every 23 liters [6 gal] of water
- Coolant Capacity (Engine Only): 4.50 liters [1.19 US Gal]
- Design fill rate 10 liters/minute [2.8 gal/min]
Full service-parts list: Cummins/Onan CFP83-F10 →, Cummins/Onan CFP83-F20 →, Cummins/Onan CFP83-F30 →, Cummins/Onan CFP83-F40 →
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.