C18 Marine Engines Coolant Level - Check Caterpillar


Coolant Level - Check
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1.1. Engines That Are Equipped with a Coolant Recovery Tank
2.1. Engines That Are Not Equipped with a Coolant Recovery Tank

Check the coolant level when the engine is stopped and cool.

Engines That Are Equipped with a Coolant Recovery Tank



    Illustration 1g00103638
    (1) Filler cap
    (2) "COLD FULL" mark
    (3) "LOW ADD" mark

  1. Observe the coolant level in the coolant recovery tank. Maintain the coolant level to "COLD FULL" mark (2) on the coolant recovery tank.

  2. Loosen filler cap (1) slowly in order to relieve any pressure. Remove the filler cap.

  3. Pour the proper coolant mixture into the tank. Refer to this Operation and Maintenance Manual, "Refill Capacities and Recommendations" for information about coolants. Do not fill the coolant recovery tank above "COLD FULL" mark (2).

  4. Clean filler cap (1) and the receptacle. Reinstall the filler cap and inspect the cooling system for leaks.

Note: The coolant will expand as the coolant heats up during normal engine operation. The additional volume will be forced into the coolant recovery tank during engine operation. When the engine is stopped and cool, the coolant will return to the engine.

Engines That Are Not Equipped with a Coolant Recovery Tank

------ WARNING! ------

Pressurized System: Hot coolant can cause serious burns. To open the cooling system filler cap, stop the engine and wait until the cooling system components are cool. Loosen the cooling system pressure cap slowly in order to relieve the pressure.


  1. Remove the cooling system filler cap slowly in order to relieve pressure.

  2. Maintain the coolant level within 13 mm (0.5 inch) of the bottom of the filler pipe. If the engine is equipped with a sight glass, maintain the coolant level to the proper level in the sight glass.


    Illustration 2g00103639
    Typical filler cap gaskets

  3. Clean the cooling system filler cap and inspect the condition of the filler cap gaskets. Replace the cooling system filler cap if the filler cap gaskets are damaged. Reinstall the cooling system filler cap.

  4. Inspect the cooling system for leaks.