Newer vehicle use a coolant temperature sensor to calculates the engine's running temperature, which adjusts itself to prevent overheating by alerting you when the engine temperature is too high. Poor fuel economy, coolant leaks, and an overheating engine are common signs of coolant sensor failure.

Sometimes, replacement is the only option, and you don't always need a mechanic to fix it. You should be able to replace the sensor yourself by following these guidelines.

Prepare to Replace the Sensor

To change the sensor, you need:

• work gloves
• eye goggles
• old container
• jack
• jack stands 
• socket and ratchet set
• plumber's tape
• coolant
• replacement coolant sensor

Let the engine cool about an hour before you make repairs, if it has been running. Park the vehicle on a flat surface that isn't a driveway, raise the front on a jack stand, and support the back wheels with jacks. 

Drain the Radiator Fluid

Draining radiator fluid helps to release vacuum pressure. Release the hood latch, prop the hood open, and locate the radiator cap; referring to your owner's manual, if needed. Unscrew the radiator cap and the overflow cap on the coolant reservoir. 

Crawl under the vehicle on the driver's side, look for two plugs, set the container under one of them, and open it. The petcock valve on the left expels the fluid slowly, and the radiator valve releases fluid in high volumes. When the coolant drains completely, reinstall the plugs and cap. Keep the coolant container out of reach of pets and children.

Replace the Sensor

Look for the coolant sensor, which is usually a square metal box, near the front upper section of the engine bay on the driver's side. On V8 engines, the sensor may be near the intake manifold. 

Press down on the safety clip with a flat-blade screwdriver to release the two wires, and push the wires aside. On some models, you may need to remove a cover. Detach the sensor with a one-fourth inch socket wrench, and use it to help buy one with the same configuration.

Wipe the space where the sensor installs with a rag since debris can lessen the functioning of the new sensor. Place plumbing tape over the threads for a tight seal.

Insert the new sensor, and twist it manually until it is even with the engine. Don't use torque on the sensor, or it could cause it to give inaccurate readings and damage the sensor. Reattach the wires, and refill the coolant, but don't attach the radiator cap yet.

Start the engine, and wait for the thermostat to open, which is commonly occurs at 195 degrees Fahrenheit. The fluid should decrease in the radiator. Also, listen for strange noises. If everything seems to be working, fill the radiator again, and attach the cap.