Coolant temperature sensor replacement

Coolant temperature sensor replacement
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This sensor controls the coolant temperature and supplies the relevant data to the engine computer. This data is used to determine the right composition of the fuel-air mix and to start the radiator fan. Its failure results in no or misleading information on the engine temperature being displayed on the dashboard. Such failure is detectable by means of a diagnostic tester. A malfunctioning sensor should be replaced with a new one.

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  • A damaged coolant temperature sensor may cause serious malfunctions. If it does not work or provides misleading information, the engine may overheat and seize, or the cylinder head may be damaged
  • When replacing the sensor check if the concentration of the coolant in the cooling system is sufficient
Range of services icon

Range of services

  • Removing a part of the coolant from the system
  • Disconnecting the sensor from the electrical system
  • Removing the sensor from the cylinder head or the radiator
  • Replacing the sensor gasket, if necessary
  • Fitting a new sensor in
  • Filling the system up with the coolant
  • Bleeding the system, if necessary

Car workshops: Coolant temperature sensor replacement

Service description

What is the role of the coolant temperature sensor?

The coolant temperature indicator on the dashboard displays the information fed to it by the coolant sensor located in the cooling system. The sensor, also referred to as the thermistor, changes its resistance depending on the temperature. When this happens, the temperature indications change.

When should the coolant temperature sensor be replaced?

Like any other electrical device, the coolant temperature sensor may brake down. It is not repairable and has to be replaced. As the sensor is washed by the coolant circulating in the cooling system, the coolant must be removed before the sensor can be replaced.

How is the coolant temperature sensor replaced?

The sensor is disconnected from the electrical system and removed from its holding element, usually the engine cylinder or one of the radiator hoses. It is replaced with a new sensor. If it comes with a gasket, it also needs replacing. Next, the cooling system is refilled with a coolant. This is a perfect opportunity to check the pressure of the coolant. A failure of the temperature sensor may result in false indications of the temperature indicator or lack of any indications at all. A failure of this component may also be detected after connecting the on-board computer to a diagnostic tester.

What to keep in mind?

Do not ignore a faulty temperature sensor. A faulty sensor will not warn you against engine overheating. It will also fail to provide the engine controller with information on the current temperature of the coolant, as a result of which wrong fuel-air mixture will be selected, increasing fuel consumption and causing wrong engine operation.

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