Regularly changing your Cummins marine engine's antifreeze (coolant) is essential for maintaining optimal engine performance and preventing overheating or corrosion. Here’s a step-by-step guide to help you safely and effectively change the antifreeze in your Cummins marine engine.

Tools and Materials Needed

• Cummins-approved antifreeze/coolant (check your owner’s manual for the correct type)

• Distilled water (if mixing coolant)

• Funnel

• Drain pan

• Wrench or socket set

• Safety gloves and goggles

• Clean rags or towels

• Coolant tester (optional, to check concentration)

Step-by-Step Instructions

1. Safety First

• Ensure the engine is completely cool before starting. Hot coolant can cause severe burns.

• Wear safety gloves and goggles to protect yourself from spills and splashes.

• Work in a well-ventilated area to avoid inhaling fumes.

2. Locate the Drain Plug

• Find the drain plug on the engine’s cooling system. It is usually located at the bottom of the radiator or engine block.

• Place a drain pan underneath to catch the old coolant.

3. Drain the Old Antifreeze

• Carefully remove the drain plug using a wrench or socket set.

• Allow the old antifreeze to drain completely into the pan.

• Once drained, securely reinstall the drain plug.

4. Flush the Cooling System (Optional but Recommended)

• If the old coolant is dirty or contaminated, flush the system with distilled water to remove any debris or residue.

  • Fill the cooling system with distilled water.

  • Run the engine for a few minutes to circulate the water.

  • Drain the water completely and repeat if necessary.

5. Refill with New Antifreeze

• Check your owner’s manual for the correct antifreeze type and mixing ratio (usually a 50/50 mix of coolant and distilled water).

• Use a funnel to pour the new antifreeze into the coolant reservoir or radiator fill point.

• Fill until the coolant reaches the recommended level (marked on the reservoir or radiator).

6. Bleed Air from the System

• Start the engine and let it run for a few minutes to circulate the new coolant and remove any air pockets.

• Check the coolant level again and top up if necessary.

• Replace the radiator or reservoir cap securely.

7. Check for Leaks

• Inspect the cooling system for any leaks around the drain plug, hoses, or connections.

• Tighten any loose fittings if needed.

8. Dispose of Old Coolant Properly

• Antifreeze is toxic and harmful to the environment. Dispose of the old coolant at a recycling center or hazardous waste facility.

Tips for Maintaining Your Cooling System

• Check the coolant level regularly and top up as needed.

• Inspect hoses and clamps for wear or damage.

• Replace the antifreeze according to the manufacturer’s recommended schedule (typically every 2-3 years or as specified in the manual).