Checking the Coolant Level
WARNING
Removing the Radiator Cap
Never attempt to remove the radiator cap while the engine is running or hot. This may cause damage to the cooling system and engine, and serious injury from hot coolant or steam being expelled.
- Turn off the engine and wait until it cools down. Be extremely careful when removing the radiator cap. Wrap it with a thick towel and turn it counterclockwise slowly to the first stop. Step back until the pressure in the cooling system is released.
When you are sure all pressure has been released, press down on the cap using a thick towel and continue turning counterclockwise to remove it. - Even if the engine is not running, do not remove the radiator cap or drain plug while the engine and radiator are hot. Hot coolant and steam may still be expelled under pressure, which can result in serious injury.
CAUTION - Cooling Fan
Use caution when working near the cooling fan blade. The electric motor (cooling fan) is controlled by engine coolant temperature, refrigerant pressure, and vehicle speed. It may sometimes run even when the engine is not running.

Inspect the condition and connections of all cooling system hoses and heater hoses. Replace any swollen or worn hoses.
The coolant level should be between the F and L marks on the side of the coolant reservoir when the engine is cold.
If the coolant level is low, add the specified coolant in sufficient quantity to ensure protection against freezing and corrosion. Bring the level up to F, but do not overfill. If frequent additions are required, have the cooling system checked by an authorized Kia dealer.
Recommended Engine Coolant
- When adding coolant, use only deionized or soft water for your vehicle, and never mix hard water with the factory-filled coolant. An improper coolant mixture may cause serious malfunction or damage to the engine.
- Your engine contains aluminum components and must be protected with ethylene glycol phosphate-based coolant to prevent corrosion and freezing.
- DO NOT USE alcohol or methanol based coolant, and do not mix them with the specified coolant.
- Do not use a solution containing more than 60% antifreeze or less than 35% antifreeze. This will reduce the effectiveness of the solution.
Refer to the following table for the mixture percentage.


WARNING
Radiator Cap
Do not remove the radiator cap when the engine and radiator are hot. Scalding hot coolant and steam may be expelled under pressure, which could cause serious injury or severe burns.
Coolant Replacement
Have the coolant replaced by an authorized Kia dealer in accordance with the Maintenance Schedule at the beginning of this chapter.
CAUTION
Before adding coolant, cover the radiator cap with a thick cloth or towel to prevent coolant from spilling onto engine components, such as the alternator.
Test yourself
A quick Kia Optima DL3 quiz: every answer comes with an explanation and a link to the manual page.