Check the condition and connections of all cooling system hoses and heater hoses. Replace any swollen or deteriorated hoses.
The coolant level should be filled between MAX and MIN marks on the side of the coolant reservoir when the engine is cool.
If the coolant level is low, add enough specified coolant to provide protection against freezing and corrosion. Bring the level to MAX, but do not overfill. If frequent additions are required, we recommend that the system be inspected by an authorized Kia dealer.
Kia Niro 2017 (DE HEV) Service Manual: Coolant Repair procedures
Refilling And Bleeding
Never remove the radiator cap when the engine is hot. Serious scalding
could be caused by hot fluid under high pressure escaping from the radiator.
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Kia Niro 2017 (DE HEV) Service Manual: Crash Pad Under Cover Repair procedures
Replacement
Put on gloves to protect your hands.
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Use a plastic panel removal tool to remove interior trim pie ...