Engine coolant temperature sensor – Learn, the right way to replace it.

Engine coolant temperature sensor - Learn, the right way to replace it.
Engine coolant temperature sensor - Learn, the right way to replace it.

The engine coolant temperature sensor, is one of the most important, engine management sensors in your vehicle.

A sensor that is shorted or reading out of range, obviously, can’t provide a reliable signal and must be replaced.

Consequently, engine coolant temperature sensor replacements, usually happens only after they have failed.

While, its function is vital, all it really does is, keep track of the changing temperatures of your engine coolant.

First, the vehicle’s (PCM/ECM) sends a 5 volt reference signal, to the engine coolant temperature sensor. Next, the resistance of that signal changes, based on the temperature, of your engine coolant. It is this resistance that the vehicle’s (PCM/ECM) monitors, to get an accurate reading, of the coolant temperature.

Sensor Temperature Resistance And Voltage Chart
Sensor Temperature Resistance And Voltage Chart

As a result, when the engine coolant temperature is high (hotter), the resistance is low. However,  when the engine coolant temperature is low (cooler), the resistance is high.

The vehicle’s (PCM/ECM) uses this information, for any or all of the following control functions:

  • Start up fuel enrichment, on fuel injected engines.
  • Spark advance and retard.
  • Exhaust gas recirculation (EGR), during warm-up.
  • Evaporative emissions control canister purge.
  • Open/closed loop feedback control of the air/fuel mixture.
  • Idle speed, during warm-up.
  • Transmission torque converter clutch lockup, during warm-up.
  • Operation of, the electric cooling fan.

Hopefully, the above list makes you realize, the importance of this basic sensor.

Now that you know its importance, we hope you have confirmed that, it is or is not working properly. If you need to do any testing please read our blog; Engine Coolant Temperature Sensor – Function, Failure And Testing. If your test was good, at least now you know what to look for in the future. A failed test confirms engine coolant temperature sensor replacement, is the next step.

Engine coolant temperature sensor replacement, is easier than you think.

Some steps and sensor locations may vary depending on the year, make and model of your vehicle. So, if you need more info, get a manual for your vehicle, as they are easy to find. And, because you already know you need a new sensor, you should get that first.

Almost every parts store has them but, I recommend you get a factory replacement from your local dealer. The biggest reason is you get what you pay for, and I would not skimp on something this important.

Engine Coolant Temperature Sensor
Engine Coolant Temperature Sensor

How To Replace, Your Engine Coolant Temperature Sensor, (Step By Step)

Step-1

  • Park your vehicle in a safe place, where you can work comfortably and let the engine cool.
  • Locate and slowly remove the cooling system pressure cap, to relieve the system of any residual pressure.
  • Place a clean drain pan under the radiator, to catch engine coolant.
  • Open the radiator valve and drain about, two to three quarts of coolant.
  • You only need to remove enough, to drop the level below the sensor.
  • Then close the drain valve. This will minimize coolant waste, when you remove the sensor.

Step-2

Removing Battery Cable From Battery
Removing Battery Cable From Battery

Step-3

  • You most likely know where the sensor is, because you already tested it.
  • But, if not, locate and get access to it.
  • You may need to remove the fan shroud or plastic engine covers, in order to get access.
  • Depending on the engine, you may have to remove, part of the plastic air intake tubing.

Step-4

  • Disconnect the engine wiring harness from the sensor.
  • A coolant sensor will be held in place, by one of two methods.
  • The most common method is similar to, installing a spark plug. Use a deep socket and ratchet wrench to loosen the sensor.
Screw In Type Sensor
Screw In Type Sensor
  • The less common method, is being held in by a large C-clip. Use a pick to pull the clip upward and away from the sensor. This will enable the sensor to be, removed from the coolant access port.
Sensor With Clip Hold Down
Sensor With Clip Hold Down

Step-5

  • Clean the hole where the sensor is located, before you reinstall the new sensor.
  • In some cases, dirt, debris, and other particles, will impact the function of the sensor.

Step-6

  • Compare the new sensor to the old one; both should have the same configuration.

Step-7

  • Time to install the new sensor (Reverse Of Step-4).
  • If the sensor uses threads; apply a small amount of (sensor safe) thread sealer to help stop coolant leaks.
  • Note: Some sensors have sealer already applied.
  • Check your manual, for proper torque specs.
  • Do not over tighten the sensor or you will crack the porcelain and damage it.
  • Some sensors are sealed by an O-ring, which requires no sealer.
  • Install the sensor by, inserting it back into the coolant access port and reinstalling the clip.
  • After the sensor has been successfully tightened, reattach the wiring harness.

Step-8

  • Once the sensor installation is complete, install any other parts you had to disassemble (Reverse Of Step-3).
  • Close the radiator drain valve and refill the system with coolant.

Step-9

  • Reconnect the battery, start the engine and make sure the “check engine” light is out.
Check Engine Light
Check Engine Light
  • Allow the engine to heat up, while adding coolant as needed.
  • Reinstall the radiator cap once the engine is at operating temperature and recheck the system for leaks.
  • Make sure the system, is blead properly to avoid air pockets.

Step-10

  • Take a test drive, while monitoring the temperature gauge, to verify a completed repair.
  • Make sure to drive the vehicle, until you hear the radiator fan come on.
  • We recommend rechecking the coolant level, after a few days of driving.

Conclusion

Sensor With O-Ring Type Of Mounting
Sensor With O-Ring Type Of Mounting

So, today’s engines monitor virtually every function to ensure your vehicle, runs strongly and efficiently every day. Consequently, one of the most important systems to monitor, is the cooling system. And, when the sensor is functioning properly; it will tell your on board computer, if the temperature is too high. Finally, alerting the driver that a problem exists, by illuminating a warning light on the dashboard.

Thank You !