To top up coolant in a 2018 Hyundai Tucson, use a 50/50 premixed ethylene glycol-based coolant that meets Hyundai’s specifications, and fill the expansion reservoir when the engine is cold. Then bleed air from the system by running the engine with the heater on until the bubbles stop, and recheck the level once the engine cools.
The 2018 Tucson relies on a closed cooling system with an overflow reservoir. This article explains how to identify the correct coolant, safely top up, bleed air, and perform post-service checks to prevent overheating and leaks.
Choose the right coolant and safety basics
Before handling the cooling system, confirm the coolant type and review safety steps. Using the correct coolant and observing proper safety measures helps protect you and the engine.
- Use a HOAT (hybrid organic acid technology) ethylene glycol–based coolant that meets Hyundai’s specification. A 50/50 premixed solution is commonly recommended for simple top-ups; avoid mixing incompatible products.
- Ensure the engine is completely cool before opening any cap. Opening a hot cooling system can cause severe burns from steam or hot coolant.
- Wear protective gloves and eye protection, work in a well-ventilated area, and keep pets and children away from the workspace.
Using the correct coolant and following safety precautions reduces the risk of engine damage and personal injury.
Top up and bleed the cooling system
These steps guide you through checking the level, adding coolant, and bleeding air from the system to prevent air pockets.
- Locate the expansion/overflow reservoir near the radiator and check the level when the engine is cold. The coolant should be between the MIN and MAX marks.
- If the level is low, prepare premixed coolant (50/50) or Hyundai Genuine Coolant per the label; if you’re using concentrate, mix it with distilled water as directed by the product instructions.
- Open the reservoir cap slowly after confirming the engine is cold, then remove it to access the reservoir.
- Pour coolant gradually into the reservoir until the level sits between the MIN and MAX lines. Do not overfill.
- Replace the reservoir cap securely and start the engine with the heater set to HOT. If needed, briefly vent by removing the radiator or reservoir cap during bleeding, then continue as directed to avoid pressure buildup.
- Let the engine run until the thermostat opens and the cooling fans operate normally. Watch for air bubbles and top off as needed until the level stabilizes near MAX, avoiding overfilling.
After bleeding, recheck the level once the engine has cooled and top off if necessary.
Post-service checks and disposal
Once you’ve topped up the coolant, perform these quick checks and follow safe disposal practices for old coolant.
- Inspect hoses, clamps, and the radiator for signs of leaks or damage; replace worn parts as needed.
- Verify there are no air pockets by letting the engine reach operating temperature and then rechecking the level after it cools.
- Dispose of any old or spilled coolant at a proper recycling facility. Do not pour coolant down the drain or on the ground; it is toxic to animals and the environment.
Regular post-service checks help maintain cooling performance and prevent overheating or leaks.
Summary
To add coolant to a 2018 Hyundai Tucson, use a 50/50 premixed HOAT ethylene glycol coolant that meets Hyundai specifications. Ensure the engine is cold before opening any caps, fill the expansion reservoir to the correct level, and bleed air by running the engine with the heater on until bubbles stop. Recheck the level after the engine cools and address any leaks or worn components promptly. Proper disposal of used coolant is essential for safety and the environment.