How to replace the coolant temperature sensor?

The coolant temperature sensor is a component of the cooling system that monitors coolant temperature and warns the driver if the engine is overheating.  Because engine temperature plays a critical role in the overall performance of any vehicle, a properly functioning coolant temperature sensor is essential. If you determine that the sensor is defective, you'll need to replace it by following the step-by-step instructions below.

When do you need to replace your coolant sensor?

Here are some of the warning signs that your coolant temperature sensor is damaged and needs to be replaced.

Low fuel economy: If you notice that the temperature warning light is on and your fuel economy is really low, it could be the sensor. When the coolant temperature sensor isn't working properly, it tends to send false information to the engine control module. This, in turn, causes the ECM to add more fuel or reduce the air mixture to create a "rich" situation, which is designed to cool the cylinders and reduce the potential for overheating. The side effect of this reaction is that fuel economy is significantly reduced.

Black exhaust smoke: When the fuel mixture is rich (i.e., there is more fuel than air in the vapor in the combustion chamber), the cylinder cannot burn all the fuel. As a result, more black smoke is emitted through the cylinder head exhaust port and exhaust pipe.

Engine overheating: The sensor may fail and be unable to monitor the engine coolant temperature. When this happens, there is a greater risk of overheating. If your engine occasionally overheats, the coolant temperature sensor may be the problem.

Coolant leaking under the engine: If you notice coolant leaking from the front of the engine, the location of the engine coolant temperature sensor may be the problem.

Removing and Replacing the Coolant Temperature Sensor

Step 1: Make sure the vehicle is on a level work surface.

Since you'll be jacking up the front of the vehicle and placing it on jack stands, make sure your vehicle is on a level surface.

Step 2: Locate the coolant temperature sensor.

The first thing you need to do is locate the coolant temperature sensor.

You can see that most coolant temperature sensors are located on the top, driver's side of the engine. However, the location of this sensor may be different on your specific engine.

Step 3: Check the clearance from the front of the vehicle.

Make sure you have enough room to slide under your vehicle.

Step 4: Remove the radiator cap and overflow cap.

Once the vehicle is lifted and you've opened the hood, the next step is to remove the radiator cap and reservoir cap. This removes the vacuum pressure in the cooling system, allowing you to drain the radiator fluid and replace the coolant temperature sensor.

Step 5: Drain the radiator.

Under your vehicle, usually on the driver's side, the radiator has two different drain plugs. One is an oil tap located on the left side of the radiator near the main drain plug.

There are two ways to drain the radiator: Either remove the gas tap and let the radiator drain slowly, or remove the radiator drain plug and expect a large amount of coolant to drain quickly.

Step 6: Replace the cap.

Once your radiator is drained, be sure to replace the drain plug or valve before continuing.

Step 7: Disconnect the electronic harness from the temperature sensor.

It's time to locate and remove the coolant temperature sensor.

The first thing to do is remove the electronic wiring harness that connects to the sensor. This sensor is usually attached with a plastic clip. To remove the clip, take a flat-bladed screwdriver and slowly pry the clip from the outer edge of the temperature sensor.

Step 8: Remove the coolant temperature sensor.

Unscrew the sensor from the engine block and remove it completely.

Step 9: Clean the sensor bore.

In some cases, dirt, debris, and other particles can interfere with the operation of the coolant temperature sensor, so make sure the area is clean before installing the new sensor.

Step 10: Install the new sensor.

Using your fingers, hand-tighten the coolant temperature sensor into its mounting hole until the sensor is level with the engine.

Remove the ratchet extension and hand-tighten the sensor using the socket and extension.

Step 11: Reattach the wiring harness to the sensor.

Once the sensor has been successfully tightened, reattach the wiring harness. It should click into place.

Step 12: Make sure the radiator drain plug is tight.

Step 13: Add coolant to the radiator.

It is highly recommended to add a new coolant. This will allow the coolant temperature sensor to function properly.

Step 14: Add coolant to the reservoir.

Once your radiator is full, you will need to add fresh coolant to your overflow reservoir.

Step 15: Remove the coolant pans.

Dispose of used coolant properly.

Step 16: Lower the vehicle from the jacks.

Lower the vehicle to the ground.

The coolant temperature sensor is an electronic device that alerts the driver when the engine is overheating. It activates the engine warning light to indicate that the coolant temperature is too high. If your coolant temperature sensor is defective, don't hesitate to shop around for a replacement.