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How to replace your car thermostat

Peter Sitkowski | 6th May 2024 | 5 minutes to read

A car's thermostat ensures the proper regulation of the engine's temperature. If your engine is warming up slowly or overheating after it reaches temperature, then your thermostat might be faulty and need replacement.

Replacing a car's thermostat is a manageable task for most car owners with basic mechanical skills and thermostats are a relatively cheap component to buy. Performing the job yourself will likely save you a decent sum of money and you're going to get more longevity out of your vehicle for a fairly low-effort fix.

Below are guidelines for replacing your thermostat, all of which should be followed in tandem with recommendations from your vehicle’s manual:

  1. Gathering Tools & Preparing the Vehicle
  2. Locating the Thermostat Housing
  3. Draining Coolant
  4. Accessing and Installing the Thermostat
  5. Reassembling Components
  6. Inspection & Checking for Leaks

Tools for the Job

  • New thermostat for vehicle make and model
  • Socket and ratchet set
  • Drain pan
  • Gasket scraper or razor blade
  • Suitable coolant
  • Goggles
  • Gloves
  • Torque wrench

Gathering Tools & Preparing the Vehicle

Before initiating the thermostat replacement, gather necessary tools and materials from the list provided.

Allow the engine to cool down completely before beginning work to prevent burns from hot components. Park the vehicle on a level surface and engage the parking brake. If necessary, raise the vehicle using a jack and support it securely with jack stands.

Locating the Thermostat Housing

Refer to the vehicle's manual or online resources to locate the thermostat housing. The thermostat is typically situated between the engine and the radiator, connected to the upper radiator hose.

Draining Coolant

Place a drain pan underneath the radiator drain plug or petcock to catch the coolant. Loosen the plug or petcock to drain the coolant into the pan. Dispose of the used coolant in accordance with local regulations.

Accessing and Installing the Thermostat

Clear any components obstructing access to the thermostat housing. This may involve removing the air intake duct, coolant hoses, or other parts in the vicinity. Exercise caution and take note of the disassembly sequence for reinstallation.

Once the area around the thermostat housing is accessible, use the appropriate tools to disconnect the upper radiator hose from the thermostat housing. Carefully remove the bolts securing the thermostat housing cover.

Removing the Old Thermostat

Gently pry out the old thermostat from its housing using a screwdriver or similar tool. Take note of the thermostat's orientation to ensure proper installation of the new one. Clean the housing surface thoroughly using a gasket scraper or razor blade.

Installing the New Thermostat

Insert the new thermostat into the housing with the correct orientation as noted earlier. Ensure it fits snugly and sits flush within the housing. Place the thermostat housing cover back in position and secure it with the bolts.

Reassembling Components

Reconnect the upper radiator hose to the thermostat housing, ensuring a secure fit. Reinstall any components previously removed, following the disassembly sequence in reverse order.

Carefully refill the radiator with the appropriate coolant mixture, following the manufacturer's recommendations for the correct coolant type and proportions. Bleed any air from the cooling system by opening the bleed valve if present.

Inspection & Checking for Leaks

Start the engine and allow it to reach operating temperature. Monitor for any signs of coolant leaks around the thermostat housing or other connections. Tighten any fittings as needed to address leaks.

Observe the engine temperature gauge to ensure it remains within the normal operating range. A functioning thermostat helps regulate the engine temperature, preventing overheating or insufficient warming.

Inspect the area around the thermostat housing for any leftover tools, debris, or spills. Dispose of any used materials responsibly and clean the work area.

Once you have cleaned down the area, you should document the thermostat replacement, including the date, parts used, and any observations made during the procedure for future reference.