Coolant Temperature – How it Works, Best Practices to Maintain It

Regulating the coolant temperature and preventing heating up through timely maintenance will keep your fleet operation cool and running. Best practices unfolded here.

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Fleet managers maintain tight timetables with limited leeway to satisfy their clients’ demanding needs and maintain the business’s productivity. Their fleet’s constant repair and care is a daily problem in keeping the firm operating. The last thing a fleet needs is unplanned downtime, which may be expensive. Choosing the appropriate lubricants and fluids and performing proper fleet maintenance are crucial to this upkeep.

One of the major factors affecting an engine’s longevity and performance is coolant temperature. In this blog, we will discuss coolant temperature, how it works, and how important it is to maintain it. In addition, we will cover software and coolant temperature sensors, which are essential components for monitoring and managing engine temperature.

What is Coolant Temperature?

The term “coolant temperature” describes the temperature of the coolant that runs through the engine’s cooling system to keep it running at a certain temperature. Coolant, which is a water and antifreeze mixture, dissipates heat from the engine’s hot metal components. Depending on the kind of engine and the environment it runs in, coolant temperatures can vary.

How Does Coolant Temperature Work?

An internal combustion engine, the kind most commonly found in vehicles, depends on liquid coolant to operate properly. Coolant is a liquid that travels throughout the engine to absorb heat from the exhaust manifold, cylinder head, and engine block, among other parts. The coolant absorbs heat and then dissipates it by the radiator, which releases it into the surrounding air.

The engine block or cylinder head contains a sensor tracking the coolant temperature. The engine control module (ECM), also known as the powertrain control module (PCM), is the computer that manages the engine’s functioning. This sensor detects the coolant’s temperature as it passes through the engine.

What Happens When Coolant Temperature Goes Up?

Although modern engines are designed to be durable, dependable, and efficient, the coolant system in your fleet vehicles may start to malfunction if the motor produces significantly higher heat than usual. This may harm the vehicle’s engine and other parts, eventually stopping the vehicle and making it unusable. There are multiple causes for a vehicle to overheat and perform below par.

• Leakage in the cooling system makes the pressure drop and reduces the boiling point of the coolant
• Radiator cap or thermostat that has gone bad or is stuck
• The water pump or drive belt has stopped functioning
• A low amount of coolant reduces the air from getting into the system
• Mechanical issues like a faulty head gasket
• Malfunctioning cooling fan and accessories
• Debris stuck in front of the radiator that is restricting the airflow

What Does the Coolant Temperature Sensor Mean?

A temperature sensor primarily tracks the engine’s performance and gives the engine control unit (ECU) feedback, which controls the engine’s temperature. The sensor measures a thermistor’s resistance, which varies with temperature. The thermistor’s resistance lowers as the engine temperature rises due to continuous driving, and the sensor transmits a signal to the ECU, which modifies the fuel mixture and other settings to maintain the desired engine temperature.

Using this data, the ECM or PCM can modify the engine’s operating parameters, including the fuel delivery quantity and ignition timing. For instance, the engine can run too high if the temperature deviates too much from the optimal range. This indicates that it will consume gasoline excessively and emit too many emissions. And a temperature that is too high can cause the engine to run too lean. This indicates that it will consume gasoline excessively, which could lead to overheating or component damage.

Types of Coolant Sensors Used in Modern Vehicles

1. Thermistor Sensor: This kind of sensor uses a thermistor, a kind of resistor that alters resistance in response to temperature variations. The thermistor’s resistance varies with coolant temperature, and this variation is used to determine the temperature.
2. Thermocouple Sensor: This type of sensor employs two wires made of different metals joined together at one end. When temperature changes occur, the sensor generates a voltage between the two wires, which is used to calculate the temperature.

3. Resistance Temperature Detector (RTD) Sensor: This type of sensor uses a wire made of a material that can change its resistance as the temperature changes.
4. Hall Effect Sensor: This type of sensor uses a magnetic field to measure temperature. The magnetic field also changes as the temperature changes and the temperature is calculated.

The type of coolant sensor used in a vehicle depends on the make and model of the vehicle and the specific requirements of that engine’s cooling system.

Importance of Maintaining Coolant Temperature

Ensuring the engine runs effectively and safely requires maintaining the proper coolant temperature. If the engine runs too hot or too cold, its lifespan might be shortened, and damage can occur. Operating the engine too cold can result in more pollutants and less fuel economy while operating it too hot might cause the engine to seize. The ideal temperature range must be maintained to guarantee that the engine runs at its best and lasts as long as possible.

Temperature monitoring is crucial to an internal combustion engine’s healthy operation. It precisely monitors and controls the cooling system and engine control system components.

Coolant Temperature Maintaining Software

Coolant temperature maintenance software is an essential component of modern engine control systems. TrackoBit is compatible with all types of coolant temperature sensors. It receives input from various sensors, including the temperature sensor. This ensures the engine operates within its desired temperature range.

Fleet maintenance with coolant alerts

Fleet management and maintenance are significant components of logistics and transportation operations. A coolant alarm is essential for this management since it helps protect your vehicles. Even though the coolant temperature has increased, there are situations in which the vehicle’s engine may not shut down. When this occurs, fleet maintenance software enables you to receive coolant notifications continuously until the problem is fixed.

TrackoBit’s solutions for high coolant temperature issues

An engine that overheats quickly is likely to suffer damage quickly. Proper maintenance and measurement are essential for the longevity of your vehicle and its engine, as well as to guarantee the simple and trouble-free operation of your cooling system.

The need is for a system that assists with careful monitoring and can prevent unwanted vehicle damage. Through TrackoBit’s dashboard, you can monitor your coolant system and ensure the temperature is kept at the ideal levels to minimise difficulties and vehicle downtime.

TrackoBit is compatible with every external coolant temperature sensor and the OBD plug that is useful in measuring engine parameters directly. The Electronic Control Unit (ECU) can provide vehicle data when the OBD tool is connected to the port. In addition to warning you when the temperature exceeds 105 degrees Celsius, TrackoBit allows you to set custom thresholds as needed. Keep track of the aforementioned reasons for variations in coolant temperature and take immediate action to address the issue by staying informed about the condition of your vehicles.

Conclusion

An engine’s ability to operate properly depends critically on the temperature of the coolant. The proper temperature range must be maintained to guarantee the engine runs effectively and safely. The coolant temperature sensor and maintenance software are crucial for tracking and controlling engine temperature. Regular cooling system maintenance and checking coolant levels are crucial to maintain the ideal engine temperature.

TrackoBit, through its preventive maintenance solution, real-time tracking and monitoring of vehicle health and temperature, and instant alerts, will help prevent the vehicle from heating up.

The ECTS may be small, but it’s built with several key components that allow it to function accurately and reliably.

At its core is the NTC thermistor, a ceramic semiconductor that changes resistance based on temperature. It typically has a resistance of 2.5-3.0 kΩ at 20 °C, with a beta value of - K, which determines how its resistance shifts as temperatures change. This relationship follows a predictable pattern where resistance decreases as temperature rises, and it is described mathematically by the Steinhart-Hart equation:

1/T=A+B(lnR)+C(lnR)3

where T is the temperature in Kelvin, R is resistance in ohms, and A, B, and C are specific to the thermistor’s material properties.

For more information, please visit Coolant Temperature Control Devices.

To ensure accurate temperature readings and long-term durability, the conductive metal housing—typically made of brass or stainless steel—protects the sensor from coolant exposure and extreme temperatures ranging from -40 °C to +130 °C.

The hexagonal corona, a 19 mm or 3/4" hex fitting, allows for precise installation, with a typical torque specification of 15-20 Nm to prevent leaks. Meanwhile, the thread, often an M12 or M14 with a 1.5 mm or 1.25 mm pitch, ensures a secure, pressure-tight seal in cooling systems that operate at 15-20 PSI.

The electrical terminal is a two-pin connector, usually made from a copper alloy with gold or tin plating to resist corrosion and maintain conductivity. As vehicles operate in demanding conditions, this terminal is designed to withstand vibrations from 10-500 Hz and temperatures up to 125 °C.

Inside the sensor, Kovar wires serve as the conductor, carefully selected for their thermal expansion properties that match glass, ensuring a hermetically sealed electrical connection. These wires typically range from 22 to 26 AWG for stable signal transmission.

The ECTS operates by generating a voltage signal based on temperature changes. The ECU supplies a reference voltage—usually 5 V—to the sensor. Inside the ECU, a voltage divider circuit pairs the ECTS with a fixed resistor. As the thermistor’s resistance changes, the voltage output shifts accordingly. This signal, typically ranging between 0.5 V and 4.5 V, is processed through the Analog-to-Digital Converter (ADC) in the ECU, which translates it into an accurate temperature reading.

With this real-time data, the ECU can make necessary engine adjustments. If the temperature changes, the ECU may modify fuel injection timing by ±5 %, advance or retard ignition timing by up to 10°, or activate the radiator fan when the coolant reaches 93-96 °C. Additionally, the ECTS helps determine when to switch the engine into closed-loop feedback control, which typically happens around 70 °C, allowing for more precise fuel and emissions management.

By continuously monitoring coolant temperature, the ECTS helps prevent overheating, optimizes engine efficiency, and protects vital components from heat-related damage. Its precise measurements and rapid response—typically under five seconds for a 63.2 % temperature step change—ensure that the engine maintains a stable temperature under varying operating conditions.

What Happens When a Coolant Sensor Fails, and How Can Faults Be Detected?

A faulty ECTS is one of the most common reasons for engine overheating. While most vehicles have dashboard alerts for high temperatures, they don’t always warn drivers when the sensor itself is malfunctioning. If the ECTS fails, the ECU might receive incorrect temperature readings, causing the engine to run too hot or too cold. This can lead to performance issues, reduced fuel efficiency, and, in some cases, serious engine damage.

A Case Sudy

To better understand these failures, a study looked into ECTS anomalies using telemetry data from a single vehicle in two different conditions—idling and driving. Researchers tested ten different one-class classifiers to see how well they could detect three levels of sensor malfunction. They developed an anomaly detection system with four main components: data acquisition, feature extraction, feature selection, and classification.

For real-world data collection, the team used an embedded system connected to the OBD-II interface of a Toyota Etios ( CC engine). A Carloop microcontroller-based development kit with cellular connectivity captured vehicle data at a rate of one sample per second (1 Hz). This setup allowed them to continuously monitor ECTS behavior and other engine parameters.

Instead of just flagging odd sensor readings, the system focused on contextual anomalies—analyzing sensor data in relation to overall vehicle performance. To do this, they used a sliding window approach for feature extraction, incorporating 27 different parameters, including the standard deviation of engine coolant temperature.

The researchers also examined seven additional vehicle parameters—engine load, RPM, long-term fuel trim, tank level, manifold absolute pressure, and catalyst temperature—to determine which factors were most relevant for detecting ECTS faults.

After analyzing the data, they found that RPM and coolant temperature were the most critical attributes, along with the standard deviation and variance of ECTS readings. To ensure accuracy, all attributes were normalized to a (0,1) scale before feeding them into the anomaly detection models.

For detecting anomalies, the researchers used one-class classification techniques. The system was trained on data from normal ECTS operation (with no active Diagnostic Trouble Codes) and then tested to see how well it could identify deviations. They evaluated various machine learning approaches, including support vector machines (SVM), rule-based systems, neural networks, statistical methods, and instance-based techniques.

The results showed that the one-class SVM with a third-degree polynomial kernel worked best for detecting anomalies while the vehicle was moving. However, when the engine was running but the car was stationary, the k-nearest neighbor (KNN) classifier performed better. These findings highlight how machine learning can help with early ECTS fault detection—potentially preventing overheating issues before they turn into serious problems.

Key Players in the ECTS Market

Several major companies are driving innovation in automotive sensor technology:

• Robert Bosch GmbH: A global leader in automotive technology, Bosch continues to develop cutting-edge sensor solutions for vehicles.
• Texas Instruments (TI): TI is advancing automotive safety and intelligence with semiconductor innovations like the AWR 77GHz millimeter-wave radar sensor, designed to enhance ADAS decision-making.
• Honeywell: Known for its broad range of sensor technologies, Honeywell remains a key player in the automotive sensor market.
• Sensata Technologies: This company is focused on advanced sensor solutions, including suspension pressure sensors for Active Suspension Systems in electric vehicles.
• NXP Semiconductors: A major force in automotive sensors, NXP is investing heavily in R&D to push the boundaries of sensor technology.

These companies are constantly working to improve sensor efficiency, accuracy, and reliability. For instance, Sensata Technologies is developing solutions to help vehicles meet stricter emissions regulations while enhancing safety features. Meanwhile, Texas Instruments is refining sensor accuracy through semiconductor advancements, as seen in their latest automotive chips aimed at improving vehicle intelligence.

With growing concerns over road safety and the rise of connected vehicle technologies, the automotive sensors market is on track to reach USD 41.08 billion by . This growth is being fueled by continuous innovation and strategic partnerships among these industry leaders.

The Bottom Line

So what is your key takeaway from this article? Your car’s ECTS is a crucial player in keeping your engine at the right temperature. By monitoring the coolant-antifreeze mixture and working with the ECU, it helps regulate fuel injection, ignition timing, and radiator function.

With ongoing research into anomaly detection and smarter sensors, drivers can look forward to even more reliable and efficient cooling systems in the future.

Want to Learn More?

Interested in other key vehicle sensors and how they impact performance? Check out these topics:

• Discover how mass airflow sensors measure the amount of air entering your engine for optimal combustion.
• Learn the difference between accelerator pedal position sensors and throttle position sensors.
• What is a knock sensor and how does it prevent engine damage by detecting abnormal combustion.

With advancements in automotive technology, sensors like the ECTS are becoming more sophisticated, ensuring better performance, efficiency, and safety. Stay informed about the latest trends and innovations to keep your vehicle running smoothly.

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