Kia Optima: Checking the Coolant Level
WARNING - Removing Radiator Cap

Check the condition and connections of all cooling system hoses and heater hoses. Replace any swollen or deteriorated hoses.
The coolant level should be full in the radiator and between F (Full) and L (Low) on the coolant reservoir tank when the engine is cool.
Check the coolant level using the dipstick attached to the reservoir cap.

If the coolant level is low, add enough coolant to bring the level to F, but do not overfill. If frequent additions are required, see an authorized Kia dealer or another competent repair center for a cooling system inspection.
Engine Cooling System
Changing CoolantTrunk Lid
To open the trunk, insert the key into the lock and turn it clockwise until
an audible “click” is heard.
To close the trunk, use both hands to push the trunk lid down until the
lock ...
Repair procedures
Inspection
1.
After disconnecting the vapor hose from the PCV valve,
remove the PCV valve. Visually check for a collapsed vapor hose or hose
leaks.
2.
...
Troubleshooting
Trouble Symptom Charts
Trouble Symptom 1
Trouble Symptom 2
Trouble symptom
Probable cause
Remedy
The set vehicle speed varies greatly ...