This procedure covers removal and replacement of the thermostat on the 2019-2024 Toyota RAV4 with the 2.5L I4 gasoline engine, including coolant drainage, housing removal, and system refill with proper bleeding.

Warnings

Tools required

Parts

• Thermostat assembly × 1 — Use OEM specification
• Thermostat housing gasket × 1 — Use OEM specification
• Lower radiator hose clamp (if damaged) × 1 — Use OEM specification

Fluids

• Toyota Super Long Life Coolant (Pink) — 2 qt

Preparation

1. Ensure engine is completely cold to the touch (minimum 2 hours after last operation)
2. Park vehicle on level surface and engage parking brake
3. Place drain pan under engine to catch coolant
4. Remove engine cover by pulling upward on front edge, then lifting away from rear mounting grommets
5. Locate thermostat housing on driver's side of engine block, near the front where the lower radiator hose connects

Procedure

1. 1

   Drain cooling system
   Slowly remove the radiator cap by turning counterclockwise to release any residual pressure. Locate the radiator drain plug at the bottom driver's side of the radiator. Place drain pan underneath and open the drain plug to drain approximately 2 quarts of coolant. If the drain plug is difficult to access, alternatively disconnect the lower radiator hose at the radiator end to drain coolant.
   ⚠Even when cold, some pressure may remain in the system. Open radiator cap slowly and stand clear of the opening.
2. 2

   Disconnect lower radiator hose
   Locate the lower radiator hose connection at the thermostat housing. Use a flathead screwdriver or pliers to loosen the hose clamp and slide it back along the hose approximately 3-4 inches. Twist the hose gently to break the seal, then pull it off the thermostat housing nipple. Allow any remaining coolant to drain into the pan.
   ℹ️The hose may be stuck due to age. Gently twist back and forth while pulling to avoid tearing the hose end.
3. 3

   Remove thermostat housing bolts
   Identify the two 10mm bolts securing the thermostat housing to the engine block. Remove both bolts completely and set aside. The housing is located at the front driver's side of the engine where the lower radiator hose connects.
4. 4

   Remove thermostat housing and old thermostat
   Carefully pull the thermostat housing away from the engine block. The thermostat is integrated into or seated within the housing. Remove the old thermostat and note its orientation - the spring side faces toward the engine block, while the valve side faces outward toward the radiator hose. Remove and discard the old gasket from the mating surface.
5. 5

   Clean mating surfaces
   Using a plastic scraper, thoroughly clean both the engine block mating surface and the thermostat housing mating surface. Remove all traces of old gasket material, coolant residue, and debris. Wipe clean with shop towels. Inspect surfaces for damage, deep scratches, or warping that could prevent proper sealing.
   ⚠Do not use metal scrapers or abrasive pads that could gouge the aluminum mating surfaces and cause leaks.
6. 6

   Install new thermostat and gasket
   Position the new gasket onto the engine block mating surface or into the thermostat housing groove (depending on design). Install the new thermostat with the spring side facing toward the engine block and the jiggle valve or air bleed positioned at the top (12 o'clock position). This orientation is critical for proper air bleeding.
   ⚠Incorrect thermostat orientation will prevent proper cooling system operation and can cause overheating or incomplete air bleeding.
7. 7

   Install thermostat housing
   Carefully position the thermostat housing over the thermostat and align it with the bolt holes on the engine block. Ensure the gasket remains properly seated and does not shift during installation. Hand-thread both 10mm housing bolts to prevent cross-threading.
   Torque spec

   Thermostat Housing Bolts15 Nm (11 lb-ft)
8. 8

   Torque housing bolts
   Using a torque wrench, tighten the thermostat housing bolts in a crisscross pattern to 14.0 Nm (10 lb-ft). This ensures even compression of the gasket and prevents distortion of the housing.
   Torque spec

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

   Reconnect lower radiator hose
   Slide the lower radiator hose back onto the thermostat housing nipple, pushing firmly until it seats completely against the housing base. Position the hose clamp over the connection point, approximately 1/4 inch from the hose end. Tighten the clamp to 4.0 Nm (3.0 lb-ft) using a torque wrench with appropriate adapter, or snug firmly with pliers if using a spring clamp.
10. 10

    Close radiator drain and refill coolant
    Close the radiator drain plug securely. Fill the cooling system through the radiator opening with Toyota Super Long Life Coolant (pink) premixed 50/50 with distilled water. Fill slowly to allow air to escape. Fill until coolant reaches the base of the radiator neck. Locate and open the bleed screw (if equipped) on the thermostat housing or nearby coolant pipe to 7.0 Nm (5.0 lb-ft) during filling to purge air. Close bleed screw when coolant flows steadily without air bubbles.
11. 11

    Bleed cooling system
    With the radiator cap still off, start the engine and allow it to idle. Set the heater to maximum temperature and fan on low. As the engine warms, the thermostat will open and coolant level will drop. Continue adding coolant to maintain level at the radiator neck. Run until the cooling fans cycle on, indicating the thermostat has opened and system is at operating temperature. Watch for steady coolant circulation and no air bubbles.
    ⚠Monitor engine temperature gauge closely. If temperature rises above normal or warning light activates, shut off engine immediately and recheck for proper installation and leaks.
12. 12

    Final fill and cap installation
    With engine still running, top off radiator to the neck and install radiator cap securely. Allow engine to cool completely. Check coolant level in the overflow reservoir and fill to the FULL cold mark. Inspect all connections at the thermostat housing and lower radiator hose for leaks.

Reassembly

1. Reinstall engine cover by aligning rear grommets first, then pressing down on front clips until secured
2. Wipe down any spilled coolant from engine bay components with clean water to prevent residue buildup

Verification

• Start engine and verify no coolant leaks at thermostat housing or lower radiator hose connection
• Allow engine to reach operating temperature and confirm cooling fans activate normally
• Check engine temperature gauge remains in normal range during idle and test drive
• Verify heat output from cabin heater is strong and consistent
• After vehicle cools completely, recheck coolant level in overflow reservoir and top off to FULL mark if needed
• Inspect under vehicle for any coolant drips or puddles after overnight parking

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