how to fix the thermostat in my Toyota Corolla E170 (2013-2019) that’s stuck open

Toyota Corolla E170 (2013-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

3 min read

557 words

Problem Statement

Learn how to fix a stuck open thermostat in a 2013-2019 Toyota Corolla E170. Step-by-step guide with symptoms, diagnostic steps, and repair instructions.

Affected Component

Cooling System

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the engine to cool before opening the radiator to prevent burns.

Symptoms

•Engine temperature gauge reading lower than normal
•Poor fuel economy
•Check engine light illuminated
•Heater not providing adequate heat
•Increased engine emissions

Diagnostic Steps

1
Scan the vehicle's onboard diagnostic system using an OBD-II scanner to check for related error codes.
2
Inspect the engine temperature gauge and confirm that it remains low during operation.
3
Visually check the thermostat housing for any signs of coolant leaks.
4
Remove the thermostat and check its operation in hot water to confirm it is stuck open.
5
Inspect the coolant level and condition in the reservoir and radiator.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Socket set
•Torque wrench
•Drain pan
•Gasket scraper
•Coolant funnel

Parts Required

•New thermostat
•Thermostat housing gasket (if applicable)
•Coolant (Toyota Long Life Coolant)

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Diagnostic Steps

1
Scan the vehicle's onboard diagnostic system using an OBD-II scanner to check for related error codes.
2
Inspect the engine temperature gauge and confirm that it remains low during operation.
3
Visually check the thermostat housing for any signs of coolant leaks.
4
Remove the thermostat and check its operation in hot water to confirm it is stuck open.
5
Inspect the coolant level and condition in the reservoir and radiator.

Solution

1. Preparation

Gather tools and parts required for the repair.
Disconnect the negative battery terminal to prevent electrical shorts.
Allow the engine to cool completely before starting the procedure.

2. Drain Coolant

Place a drain pan under the radiator.
Open the radiator drain valve and drain the coolant into the pan.
Close the drain valve once the coolant has been fully drained.

3. Remove Thermostat

Locate the thermostat housing, typically found near the engine block.
Remove the bolts securing the thermostat housing using a socket set.
Carefully lift the housing off to access the thermostat.
Remove the old thermostat from its housing.

4. Install New Thermostat

Clean the thermostat housing and engine mating surface to remove old gasket material.
Place the new thermostat in the housing, ensuring it is oriented correctly (check for a jiggle valve).
Apply a thin layer of gasket maker or install a new gasket on the housing if necessary.
Reattach the thermostat housing and tighten the bolts to the manufacturer's torque specification (typically around 10-15 ft-lbs).

5. Refill Coolant

Close the radiator drain valve.
Refill the radiator and reservoir with the appropriate coolant type as specified in the owner’s manual (typically Toyota Long Life Coolant).
Start the engine and allow it to reach operating temperature, checking for leaks around the thermostat housing.

6. Final Checks

Once the engine is at normal operating temperature, check the heater operation to ensure adequate heat is produced.
Reconnect the negative battery terminal.