Thermostat stuck Corolla E170

Tools Required

• OBD-II scanner
• Infrared thermometer
• Socket set
• Screwdriver set
• Drain pan

Procedure

1. OBD-II Scan:

   • Connect the OBD-II scanner to the vehicle’s diagnostic port.
   • Check for any fault codes related to the cooling system, such as P0128 (Coolant Thermostat Malfunction).

2. Visual Inspection:

   • Inspect the radiator and hoses for leaks or damage.
   • Check the coolant level in the radiator and overflow reservoir.

3. Temperature Check:

   • Start the engine and allow it to reach operating temperature.
   • Use an infrared thermometer to measure the upper and lower radiator hoses' temperature.
   • If the thermostat is stuck closed, the lower radiator hose will remain cool while the upper is hot.

Repair Instructions

Tools Required

• New thermostat and gasket
• Ratchet and socket set
• Torque wrench
• Coolant
• Funnel
• Pliers
• Gasket scraper or razor blade

Replacement Procedure

1. Preparation:

   • Park the vehicle on a level surface and ensure the engine is cool.
   • Disconnect the negative battery terminal to prevent electrical shorts.

2. Drain Coolant:

   • Place a drain pan under the radiator.
   • Open the radiator drain valve or remove the lower radiator hose to drain the coolant.

3. Remove Thermostat Housing:

   • Locate the thermostat housing by following the upper radiator hose to the engine block.
   • Use a socket and ratchet to remove the bolts securing the thermostat housing.

4. Remove Old Thermostat:

   • Note the orientation of the old thermostat.
   • Remove the thermostat and gasket carefully to avoid damage to the housing surface.

5. Install New Thermostat:

   • Clean the thermostat housing surface with a gasket scraper or razor blade.
   • Install the new thermostat with the spring side facing the engine.
   • Place the new gasket on the housing.

6. Reassemble Housing:

   • Secure the thermostat housing with bolts. Torque them to the manufacturer's specifications (typically 80-100 in-lbs, but check your manual).

7. Refill Coolant:

   • Close the radiator drain valve or reattach the lower radiator hose.
   • Use a funnel to refill the radiator with the appropriate mixture of coolant and water.

8. Bleed the Cooling System:

   • Start the engine and allow it to run with the radiator cap off to let air escape.
   • Once air bubbles stop and the coolant level stabilizes, replace the radiator cap.

9. Final Checks:

   • Reconnect the negative battery terminal.
   • Check for leaks around the thermostat housing.
   • Test drive the vehicle and monitor the temperature gauge for normal operation.

By following these steps, you should resolve the issue of a stuck thermostat in a Toyota Corolla E170. Always refer to the vehicle’s service manual for specific details and torque specifications.