Replace the thermostat and housing gasket on a 2015 Kia Forte 1.8L I4 engine to restore proper cooling system temperature regulation.

Warnings

Tools required

Parts

• Thermostat × 1 — Use OEM specification
• Thermostat housing gasket × 1 — Use OEM specification

Fluids

• Hyundai/Kia Long Life Coolant (Green) — 2 qt

Preparation

1. Ensure engine is completely cold before beginning work
2. Park vehicle on level ground and apply parking brake
3. Place drain pan under the engine to catch coolant
4. Remove engine cover if equipped by pulling upward on cover clips

Procedure

1. 1

   Drain coolant from system
   Locate the radiator drain plug at the bottom of the radiator on the driver's side. Slowly open the radiator cap to relieve any residual pressure, then open the drain plug and allow approximately 2 quarts of coolant to drain into the pan. You do not need to drain the entire system, just enough to drop the level below the thermostat housing.
2. 2

   Disconnect upper radiator hose
   Locate the upper radiator hose connection at the thermostat housing on the passenger side of the engine. Use a flathead screwdriver to loosen the hose clamp, then slide the clamp back along the hose. Twist and pull the hose off the thermostat housing neck. Be prepared for residual coolant spillage.
3. 3

   Remove thermostat housing bolts
   Locate the two 10mm bolts securing the thermostat housing to the engine block. Remove both bolts completely using a 10mm socket and ratchet. Keep track of the bolts as they will be reused.
4. 4

   Remove thermostat housing and old thermostat
   Carefully pull the thermostat housing away from the engine block. The thermostat will either come out with the housing or remain in the engine block recess. Remove the old thermostat and note its orientation - the spring side faces toward the engine block. Remove and discard the old gasket from both the housing and engine block mating surfaces.
5. 5

   Clean mating surfaces
   Thoroughly clean both the thermostat housing mating surface and the engine block mating surface using a plastic scraper. Remove all traces of old gasket material. Wipe surfaces clean with a shop towel and brake cleaner to ensure a proper seal. Do not gouge or scratch the aluminum surfaces.
6. 6

   Install new thermostat
   Place the new thermostat into the recess in the engine block with the spring side facing into the engine block and the bleeder valve or jiggle pin positioned at the top (12 o'clock position). Ensure the thermostat seats fully in the recess.
7. 7

   Install new gasket and housing
   Position the new gasket onto the engine block, aligning it with the dowel pins or alignment features. Carefully position the thermostat housing over the thermostat and gasket, ensuring proper alignment. Start both bolts by hand to ensure proper threading.
8. 8

   Torque housing bolts
   Using a torque wrench, tighten the thermostat housing bolts in a criss-cross pattern to the specified torque of 14 Nm (10 lb-ft). Do not overtighten as this can crack the housing or damage the gasket.
   Torque spec

   Thermostat Housing Bolts15 Nm (11 lb-ft)
9. 9

   Reconnect upper radiator hose
   Slide the upper radiator hose back onto the thermostat housing neck, ensuring it is fully seated. Position the hose clamp over the connection point and tighten to 4.0 Nm (3.0 lb-ft) using a torque wrench or snug firmly by hand.
10. 10

    Close drain plug and refill coolant
    Close the radiator drain plug securely. Refill the cooling system through the radiator cap and coolant reservoir with Hyundai/Kia Long Life Coolant (Green) mixed 50/50 with distilled water. Fill the radiator to the top and the reservoir to the MAX line. Add approximately 2 quarts total to replace what was drained.
11. 11

    Bleed cooling system
    With the radiator cap off, start the engine and allow it to idle. Turn the heater to maximum heat. As the engine warms, the thermostat will open and coolant level will drop. Continue adding coolant as needed to maintain level. Watch for coolant circulation in the radiator. Once the engine reaches operating temperature and the upper radiator hose is hot, turn off the engine.
12. 12

    Final coolant level check
    After the engine cools for 15-20 minutes, recheck coolant level in both the radiator and reservoir. Top off as necessary to the MAX line on the reservoir. Install the radiator cap securely. Reinstall the engine cover if equipped.

Reassembly

1. Ensure all hose clamps are properly tightened and positioned
2. Verify no coolant leaks are present around the thermostat housing
3. Clean up any spilled coolant from engine bay and surrounding areas
4. Properly dispose of used coolant according to local regulations

Verification

• Start the engine and allow it to reach operating temperature while monitoring for leaks around the thermostat housing
• Verify the upper radiator hose becomes hot, indicating the thermostat is opening properly
• Check that the temperature gauge reads in the normal range and does not overheat
• Confirm heater produces hot air when set to maximum temperature
• Recheck coolant level after the first drive cycle and top off if necessary

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