Replace the thermostat and housing gasket on the 2012-2018 Jeep Wrangler 3.6L V6 engine to restore proper coolant temperature regulation.

Warnings

Tools required

Parts

• Thermostat (195°F/91°C OEM specification) × 1 — Use OEM specification
• Thermostat housing gasket × 1 — Use OEM specification
• Hose clamps (if corroded or damaged) × 2 — Use OEM specification

Fluids

• Mopar OAT Coolant (Purple) — 2 qt

Preparation

1. Ensure engine is completely cold to the touch (wait minimum 2 hours after last operation)
2. Park vehicle on level ground and apply parking brake
3. Place drain pan under radiator drain petcock located on driver side lower radiator tank
4. Remove engine cover by pulling upward on all four corners to release grommets
5. Verify you have correct replacement thermostat (195°F/91°C) and new gasket

Procedure

1. 1

   Drain cooling system
   Open the radiator drain petcock by turning counterclockwise (hand tight only) and drain approximately 2-3 quarts of coolant into the drain pan. You do not need to drain the entire system, just enough to drop the level below the thermostat housing. Close the petcock when coolant stops flowing.
2. 2

   Remove upper radiator hose from thermostat housing
   Locate the thermostat housing on the lower front of the engine. Use a 10mm socket to loosen the hose clamp on the upper radiator hose where it connects to the thermostat housing. Slide the clamp back along the hose, then twist and pull the hose off the housing neck. Be prepared for residual coolant spillage.
3. 3

   Disconnect lower coolant hose
   Loosen the hose clamp on the lower coolant hose connection to the thermostat housing using a 10mm socket. Twist and remove the hose from the housing. Allow any remaining coolant to drain into your pan.
4. 4

   Remove thermostat housing bolts
   Using an 8mm socket, remove the two bolts securing the thermostat housing to the engine block. Support the housing as you remove the second bolt to prevent it from dropping. Note the bolt locations for reinstallation.
   ⚠These bolts thread into aluminum. Do not force if resistance is felt during removal as threads may be corroded.
   Torque spec

   Thermostat Housing Bolts15 Nm (11 lb-ft)
5. 5

   Remove thermostat housing and old thermostat
   Pull the thermostat housing away from the engine block. The thermostat will either stay in the housing or remain in the engine block recess. Remove the thermostat and note its orientation - the spring side faces toward the engine block. Remove and discard the old gasket from both the housing and block mating surfaces.
6. 6

   Clean mating surfaces
   Using a plastic scraper, carefully clean all old gasket material from both the thermostat housing and engine block mating surfaces. Surfaces must be completely clean and dry for proper seal. Wipe clean with a shop towel. Inspect for any damage, cracks, or corrosion.
   ⚠Do not use metal scrapers or abrasive pads on aluminum surfaces as gouges will cause coolant leaks.
7. 7

   Install new thermostat
   Place the new thermostat into the recess in the engine block with the spring side facing INTO the engine (toward the block). Ensure the thermostat seats fully and the alignment notch (if equipped) is properly positioned. The thermostat should sit flat in its recess.
8. 8

   Install new gasket and housing
   Position the new gasket onto the engine block mating surface around the thermostat. Align the thermostat housing over the thermostat and gasket, ensuring the hose connections are oriented correctly. Start both housing bolts by hand to ensure proper thread engagement before tightening.
9. 9

   Torque thermostat housing bolts
   Using a torque wrench and 8mm socket, torque both thermostat housing bolts to 15.0 Nm (11.0 lb-ft) in a criss-cross pattern. Tighten gradually and evenly - do not fully torque one bolt before starting the other. Verify both bolts are properly seated and torqued.
   ⚠These are CRITICAL torque specifications. Over-torquing will strip aluminum threads. Under-torquing will cause coolant leaks.
   Torque spec

   Thermostat Housing Bolts15 Nm (11 lb-ft)
10. 10

    Reconnect coolant hoses
    Reconnect the lower coolant hose to the thermostat housing, ensuring it is fully seated on the neck. Position the hose clamp over the connection area and torque to 4.0 Nm (3.0 lb-ft). Repeat for the upper radiator hose. Ensure hoses are not kinked or twisted.
11. 11

    Refill cooling system
    Locate the coolant fill/overflow reservoir on the passenger side of the engine bay. Slowly add Mopar OAT Purple coolant until the level reaches the MAX cold fill line. If equipped, open the bleed screw on the thermostat housing or upper coolant outlet while filling to release trapped air, then close when steady coolant flow appears.
    ⚠Only use Mopar OAT Purple coolant. Using incorrect coolant will void warranty and can cause cooling system damage.
12. 12

    Bleed cooling system and check for leaks
    Start the engine and allow it to reach normal operating temperature (approximately 195°F) with the heater set to maximum heat. Monitor the coolant level and add as needed. Watch for leaks around the thermostat housing. The upper radiator hose should become hot when the thermostat opens (approximately 5-10 minutes of running). Shut off engine and allow to cool, then recheck coolant level and top off to MAX line if needed.

Reassembly

1. Reinstall engine cover by aligning grommets with mounting posts and pressing down firmly until all four corners click into place
2. Wipe up any spilled coolant from engine bay and ground to prevent staining and environmental contamination
3. Dispose of old coolant properly at a recycling center - do not pour down drains

Verification

• Start engine and verify it reaches normal operating temperature (approximately halfway on gauge) within 5-10 minutes
• Confirm upper radiator hose becomes hot when thermostat opens, indicating proper coolant circulation
• Check for any coolant leaks around thermostat housing and hose connections with engine at operating temperature
• Verify heater produces hot air at maximum setting
• After first drive cycle, recheck coolant level when cold and top off if necessary
• Monitor temperature gauge over next several days to ensure engine maintains proper operating temperature

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