The Engine Thermostat: Understanding Electronically Assisted Thermostats -

The Engine Thermostat: Understanding Electronically Assisted Thermostats

The engine thermostat has been an important component in automotive internal combustion engines for almost a century. The engine thermostat helps to speed warmup and reduce cylinder ring wear. Today, the engine thermostat plays an important role in increasing engine combustion efficiency and reducing emissions. To accomplish that task, engine thermostat functions are controlled by the engine’s electronic control unit (ECU), ensuring precise regulation of temperature based on the engine's loads.
Fig. 1: Typical operating map for a sports car. To set the optimal coolant temperature for the corresponding operating condition, there are various predefined “if-then” situations available in the engine control unit (set points). The ideal coolant temperature can be derived from the load and vehicle speed.
Fig. 1: Typical operating map for a sports car. To set the optimal coolant temperature for the corresponding operating condition, there are various predefined “if-then” situations available in the engine control unit (set points). The ideal coolant temperature can be derived from the load and vehicle speed.

The engine thermostat has been an important component in automotive internal combustion engines for almost a century. The engine thermostat helps to speed warmup and reduce cylinder ring wear. Today, the engine thermostat plays an important role in increasing engine combustion efficiency and reducing emissions. To accomplish that task, engine thermostat functions are controlled by the engine’s electronic control unit (ECU), ensuring precise regulation of temperature based on the engine’s loads.

An electrically assisted (also called “map-controlled”) thermostat provides broader and faster operation than the traditional engine thermostat. In addition to the mechanical function of the wax element, electrically assisted thermostats incorporate an electric heater within the sensor. This heater is controlled by the vehicle’s ECU, which receives information on the speed and load conditions of the engine. It uses this information to regulate the temperature of the coolant. A data set, or “map,” is stored within the ECU to govern when and how heat is added to ensure optimal engine performance.

The experts at MAHLE Aftermarket offer these tech tips for working with electrically assisted thermostats:

• As is the case with the conventional engine thermostat, electrically assisted thermostats are not subject to material wear; they are maintenance-free and designed to last for the entire engine service life. However, external factors such as the use of low-grade coolant, and failure to regularly service the coolant can lead to material failure.

• Other possible causes of engine thermostat failure include previous damage caused by thermal overloading or contamination due to work carried out on the cooling system, for example when replacing the coolant or water pump, the cooler, the coolant hose, timing belt or V-belt.

Fig. 2: Cross section of a map-controlled thermostat with electrical connections and heating resistor integrated in the wax element.
Fig. 2: Cross section of a map-controlled thermostat with electrical connections and heating resistor integrated in the wax element.

• It is important for technicians to remember that the map-controlled thermostat is only part of a more complex cooling system consisting of coolant passages in the engine, a coolant mixing chamber around the thermostat, coolant hoses, a radiator, electric fans and the actual coolant.

• When replacing faulty parts in the cooling system, thermostats and/or integral thermostatic housings should also always be replaced at the same time because any loss of functionality (or even complete failure) can have severe consequences, including engine damage.

Courtesy of MAHLE Aftermarket Inc. 

You May Also Like

Spark Plug Replacement

Here are some tips to follow when replacing a spark plug.

Every time a spark plug fires, the spark burns a few molecules of metal off the plug’s electrodes. Over time, this eats away the electrodes and rounds off their sharp edges. The erosion gradually increases the gap between the electrodes, which, in turn, increases the firing voltage required to generate a spark. Eventually, the point is reached where the ignition system fails to produce enough voltage and the plug misfires.

Transmission Fluid Hydraulics

You need to know how transmission fluid flows inside an automatic transmission.

How ADAS Systems Perform

When new technologies are applied to driver safety, a higher level of scrutiny and service is required.

Air Ride Suspension Diagnostics

The key to understanding the embedded logic of air ride systems is using service information.

Steering Angle Sensor 101

The steering angle is used by many ADAS functions.

Other Posts
BMW N54 Turbo Problems

Here are some common problems or failures that you should be on the lookout for.

Mercedes-Benz Engine Oil Leaks

Mercedes makes a fine product, but certain repairs will emerge as trends over time.

Brake Pad Wear Sensors

Brake pad wear sensors have been around for years and continue to evolve.

Turbocharger Topics

Turbochargers have made a comeback – and it’s been quick.