Replacing the coolant temperature sensor

Coolant temperature sensor - is part of the electrical equipment of the car, which is part of the cooling system. The sensor transmits signals about the temperature of the coolant (usually antifreeze) to the engine control unit and, depending on the readings, the air-fuel mixture changes (when the engine starts, the mixture should be richer, when the engine is warm, the mixture will be poorer on the contrary), ignition angles.

Temperature sensor on the dashboard Mercedes Benz W210

Modern sensors are so-called thermistors - resistors that change their resistance depending on the supplied temperature.

Replacing the engine temperature sensor

Consider replacing the coolant temperature sensor using the example of a Mercedes Benz E240 with an M112 engine. Previously, for this car, such problems were considered: caliper repairand replacement of low beam bulbs. By and large, the algorithm of actions on most cars will be similar, it is only important to know where the sensor is installed on your car. The most likely installation locations: the engine itself (cylinder head - cylinder head), housing thermostat.

Algorithm for replacing the coolant temperature sensor

• Step 1. The coolant must be drained. This must be done on a cold engine or slightly warmed up, otherwise you can burn yourself when draining the fluid, since it is under pressure in the system (as a rule, the pressure can be released by carefully unscrewing the expansion tank cap). On a Mercedes E240, the radiator drain plug is on the left in the direction of travel. Before unscrewing the cap, prepare containers with a total volume of ~ 10 liters, this is how much will be in the system. (try to minimize the loss of fluid, since we will re-fill it into the system).
• Step 2. After the antifreeze is drained, you can start removing and replacement of the temperature sensor... To do this, remove the connector from the sensor (see photo). Next, you need to pull out the mounting bracket. It is pulled up, you can pick it up with an ordinary screwdriver. Be careful not to break the sensor when removing the bracket.
• Remove the connector from the temperature sensor
• 
• Removing the bracket holding the sensor
• Step 3. After pulling out the bracket, the sensor can be pulled out (it is not screwed in, but simply inserted). But here one problem can await. Over time, the plastic part of the sensor becomes very fragile under the influence of high temperatures and if you try to pull the sensor out with pliers, for example, the sensor will most likely crumble and only the inner metal part will remain. In this case, you can use the following method: you need to lower the upper (interfering) timing belt roller, carefully drill a hole in the sensor in order to screw a screw into it and then pull it out. ATTENTION!!! This procedure is dangerous, since the inner part of the sensor can split at any time and fall into the channel of the engine cooling system, in this case it is impossible to do without disassembling the engine. Be careful.
• Step 4. The installation of a new temperature sensor is carried out in the same way in the reverse order. Below is the catalog number of the original temperature sensor for a Mercedes w210 E240, as well as analogues.

Genuine Mercedes temperature sensor - number A 000 542 51 18

Original Mercedes Coolant Temperature Gauge

Identical analogue - number 400873885 manufacturer: Hans Pries

Comment! After you close the drain plug of the radiator and fill in antifreeze, start the car without closing the lid, warm it up at medium speed to a temperature of 60-70 degrees, adding antifreeze as it goes into the system, and then close the lid. Done!

A successful solution to the problem.

Questions and answers:

Do I need to drain the antifreeze when replacing the coolant temperature sensor? To measure the coolant temperature, this sensor is in direct contact with the antifreeze. Therefore, without draining the antifreeze, it will not work to replace the DTOZH (when dismantling the coolant sensor, it will still flow out).

When to change the coolant sensor? If the car boils, and the temperature is not indicated on the tidy, then the sensor is checked (in hot water - the resistance corresponding to the specific sensor should appear on the multimeter).