Coolant Temperature Sensor Functions and Malfunction Symptoms

Last Updated on January 16, 2019

Your vehicle’s engine can get very hot during the day. Several liquids pass through the engine and help to keep it cool. The water in the radiator runs through the pipes and maintains the temperature levels on hot days. Most common synthetic engine oils are also designed to keep your vehicle’s engine running at manageable temperatures. If you open the hood of the car, you may notice a small opening where you put the water in the radiator. On your left is the pipe that leads straight to the water supply in the windshield sprinkler.

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Coolant Temperature Sensor Function

Just adjacent to the radiator on the right side of the car is a coolant container. Your engine produces a huge amount of energy by burning fuel. Unless you use proper coolant with your car, the engine may heat up considerably during the summer months. The coolant is designed to regulate the temperature of your car. Your car is fitted with a coolant temperature sensor that keeps a check on the temperature of the coolant in the car. The main function of the temperature sensor is to make sure that the temperature of the coolant in the engine does not exceed a certain limit.

Read also:  Negative and Positive Camber Symptoms in Your Vehicle

Bad Coolant Temperature Sensor Symptoms

However, most people don’t realize that the temperature sensor may be malfunctioning. Here are just some of the major problem symptoms you should know about:

Poor Fuel Economy

Perhaps one of the biggest indicators of a malfunctioning temperature sensor is when your car begins using up more fuel than usual. Fuel-efficient vehicles are fitted with numerous electrical components that are designed to work together in order to provide a smooth drive while putting as little load on the engine as possible. The coolant is responsible for keeping the engine cool and helping it warm up when you first start your car. If the temperature sensor isn’t functioning properly, the fuel economy of your car may suffer drastically.

Black Smoke

Another telltale sign of a bad coolant temperature sensor is when your car starts releasing black smoke. There are several reasons your car may begin to emit black smoke. It may indicate an issue with the MAP sensor or the temperature sensor. Basically, black smoke means that the car’s engine is running at a much hotter temperature than it should, which is why the car is burning more fuel than what’s necessary. Professional mechanics generally have electronic diagnostic tools that are able to provide the readings needed to determine whether the coolant sensor is working properly.

Engine Overheats

Perhaps the most obvious sign that your temperature sensor needs replacement is when your engine begins to overheat after a short while. Do you notice the temperature spiking up when you turn on the air conditioner, or drive around on long trips? An overheating engine can significantly reduce the useful life of your vehicle, and may cost you a fortune in repairs, so get it checked as soon as possible!



  1. My camry 1994 model is raising idle speed when the coolant sensor is connected. When I disconnect the idle comes down but engine idling becomes erratic. What could be the problem?


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