How to Replace Thermostat 05-11 Honda Civic

Introduction

This tutorial provides a step-by-step guide on how to replace a thermostat in a 2005-2011 Honda Civic. Whether your thermostat is leaking or malfunctioning, following these instructions will help you perform the replacement safely and efficiently.

Step 1: Prepare for the Replacement

• Open the hood of your Honda Civic and secure it with the prop rod. You can adjust the rod to lift the hood vertically for better access.
• Raise the front of the vehicle using a floor jack and secure it with jack stands. This will allow you to access the radiator drain.

Step 2: Drain the Coolant

• Locate the radiator drain, which is typically found at the bottom of the radiator.
• If the drain is tight, use needle nose pliers to loosen it.
• Position a drain pan beneath the radiator to catch the coolant.
• Open the radiator cap from the top to help coolant drain faster.
• After draining, reinstall the radiator drain plug by hand to avoid over-tightening.

Step 3: Remove the Thermostat

• Locate the thermostat in the lower radiator hose.
• Remove the upper radiator hose for better visibility (this is optional but recommended).
• Use a 10mm socket and ratchet to remove the two bolts that hold the thermostat in place.
• Also, remove the two bolts on the bracket holding the sensor wires.
• Carefully pull out the thermostat. You may need to use a flat blade screwdriver to break the seal if it is stuck.

Step 4: Install the New Thermostat

• Clean the area around the thermostat seal to ensure a proper fit.
• Position the new thermostat so that the weep hole faces upwards and the rubber bumps align with the openings in the casting.
• Reinsert the thermostat into its housing.

Step 5: Reassemble Components

• Reinstall the lower gooseneck and secure it with bolts. Tighten evenly to avoid cracking.
• Reattach the bracket with the sensor wires and tight the bolts.
• If you removed the upper radiator hose, reattach it now.

Step 6: Refill the Cooling System

• Use a special radiator funnel to fill the system with a 50/50 mix of coolant and water.
• Squeeze the upper and lower radiator hoses to help remove air bubbles in the system.
• Start the engine and let it run until the thermostat opens. Watch for air bubbles escaping from the funnel.

Step 7: Finalize the Process

• Once the engine reaches temperature, shut it off and let it cool.
• Check the coolant level in the radiator and fill the reservoir to the high mark if necessary.
• Remove the funnel and reinstall the radiator cap, wiping up any spilled coolant.

Conclusion

Replacing the thermostat in your Honda Civic can be a straightforward process if you follow these steps. Regular maintenance of your vehicle's cooling system is essential for optimal performance. If you encounter any issues during the replacement, consult a professional mechanic or refer to your vehicle’s manual for further guidance.