In today's modern vehicles, the coolant temperature sensor is what tells the car's computer the current engine temperature. It works to help start the vehicle on cold days and keep it running smoothly, while also keeping the temperature regulated so it does not overheat. In older cars this would be known as the thermostat. When the coolant temperature sensor is not working properly the car will run sluggishly and could overheat. Replacing this sensor is an easy project that can be done in your own garage or on a flat driveway.
Step 1 - Open Car Hood
On a newer car, locate the hood release beneath the steering wheel inside the car. Next, put your hand in the gap under the center of the hood to feel for the latch. Push it to the side and open the hood. Use the hood support to make sure that the hood is secure and will not fall on you when you let go of it.
Step 2 - Locate Coolant Temperature Sensor
The coolant temperature sensor is located on the front of the engine block. This will vary on some cars where the pulleys are located on the side of the vehicle. However, the sensor is still located amongst the pulley system. Hold a drop light over the area and locate the sensor. You may need to remove the fan shroud in order to see into the space. The sensor will have a terminal exposed with a single wire coming from it.
Step 3 - Remove Lead Wire from Terminal
The sensor sends its signals along a lone lead wire that is located at the top of the terminal. Depending on how this is attached you will need to take care when removing it. If there are any problems with the wire you will need to replace it. Pry off the clips with a flat screwdriver without breaking the tabs. Pull the wire and set it in a place where it is out of the way.
Step 4 - Loosen Coolant Sensor
The coolant temperature sensor is installed much like a spark plug. Use a deep socket and ratchet wrench to loosen the sensor. Gradually apply pressure to the sensor while turning it in a counterclockwise direction. This will help to ensure you do not break the sensor in the threads.
Step 5 - Remove and Replace
Continue to loosen the coolant temperature sensor until you can remove it. Clean off the area and the threads with a clean shop rag. Make sure that the area is clear of any debris so it will not interfere with the replacement. Set the new sensor into the threads and begin to twist it by hand.
Step 6 - Torque Sensor in Place
Twist the coolant sensor with your fingers until you can tighten it by hand. Look up the amount of torque the sensor must be tightened to and set the torque wrench. Attach the torque wrench to the sensor and tighten it down.
Step 7 - Reconnect Wire
With the coolant temperature sensor installed you only need to reconnect the lead wire. Make sure the end of the wire is clean and plug it back into the terminal end of the sensor. Make sure it is connected tightly. Replace any other parts you had to disassemble. Turn the engine on and let it get up to operating temperature. Listen for any fluctuations in the engine and watch the temperature gauge.