MAHLE Aftermarket technology: Thermostats, the managers of the cooling circuit
To operate efficiently while minimizing wear and emissions, a combustion engine requires the temperature to remain as constant as possible. Thermostats are used exactly for that purpose, as they regulate the engine temperature with coolant.
A multitude of thermostats and other components for temperature regulation are added to complete the MAHLE Aftermarket product range:
- Expansion elements
The core of the thermostat: when heated, the expansion element (wax) expands and thus moves the piston. If the temperature drops again, it reduces in size, and a spring pushes the piston back into its starting position. Expansion elements are maintenance-free and durable. Their range of use is very versatile: actuation forces from 30 N to 2,500 N, short or long strokes, and a diversity of control ranges within the temperature span of –20°C to +130°C.
- Thermostat inserts
Precision at work: thermostat inserts enable the precise regulation of coolant circuits to approximately 20 m3/h in passenger cars, commercial vehicles, stationary engines, agricultural and construction machinery.
- Integral thermostats
The on-going development of thermostat inserts: all components such as the thermostat insert, cover, and gasket are already integrated in the integral thermostat. It can be flanged-mounted directly on to the engine block.
- Housing thermostats
These can be fully connected with hoses or equipped with a flange and hose connectors. What sets them apart is that they consist of a combination of cover and housing, i.e. the mixing chamber is already integrated.
- Map-controlled thermostats
The most effective managers in the thermal system: an electrical heating resistor is integrated in the operating element’s expansion material. Consequently, these thermostats can be electrically activated, and thereby have a considerably faster effect on the engine temperature to keep the engine within the optimum range in various load and operating conditions. The result: more engine output with reduced consumption and emissions. An operating map stored in the engine control unit defines when and how heat is added.
- Sleeve valve thermostats
The workhorses: they regulate the cooling circuits in large engines with flow volumes starting from approximately 20 m3/h, e.g. in large passenger cars, commercial vehicles, ships, and locomotives. The sleeve valve principle allows the axial relief of the thermal expansion element and thus enables precise regulation even under heavy hydraulic loads—with a consistently high level of functional safety.
- Thermal switches
Provide reliable protection against engine overheating while the vehicle is stationary: thermal switches open or close the electrical circuit, e.g. on a cooling fan, at a defined coolant temperature. The thermal switches from MAHLE Aftermarket are designed for an operating voltage of up to 24 V.
Extremely heat-sensitive: thermocouples supply data to the electronic control unit about the current temperature level at various points in the engine.
- Oil thermostats
The oil temperature in automatic transmissions is regulated by transmission oil thermostats. This shortens the warm-up phase considerably and the transmission is subsequently kept at an ideal operating temperature. The result: reduced wear, improved gearshift comfort, and fuel savings of approximately 1% in conventional driving cycles.
- EGR thermostats
These regulate the flow of coolant through the EGR cooler, thus differentiating themselves from the remaining thermostats of the MAHLE Aftermarket portfolio in terms of area of application.
Although thermostats are not standard wearing parts, there is considerable demand for spares. Whether due to an accident or as part of repair or maintenance work that requires access to the cooling system: these important temperature regulators should be replaced at that time to ensure continued functionality, because any loss of functionality or even complete failure can have severe consequences. If the thermostat is always open, the engine will be cooled too much. If the thermostat is always closed, then the engine will not be cooled at all and will overheat.
Sales identifiers and derived product abbreviations
|English sales identifier||International sales identifier||Abbreviation|
|Thermostat insert||Thermostat insert||TX|
|Sleeve valve thermostat||Thermostat, Heavy Duty||THD|
|Thermostat housing||Thermostat, Housing||TH|
|Integral thermostat||Thermostat, Integral||TI|
|Characteristic map thermostat||Thermostat, Map-controlled||TM|
|Thermal switch||Temperature SWitch||TSW|
|Operating element||Thermostat, Wax Element||TWX|
|Oil thermostat||Thermostat, Oil||TO|
|EGR thermostat||Thermostat, EGR||TE|
X = insert
The system of sales identifier and derived product abbreviation is already established in the filter segment: the sales identifier symbol is followed by the sequential number, opening temperature, and, ultimately, information about any separately enclosed gasket—identifiable by the letter “D”. The sleeve valve thermostat with the serial number 159, an opening temperature of 87°C, and an enclosed gasket is identified as “THD 159 87 D”.
With MAHLE Aftermarket assuming responsibility for the sales activities for Behr Thermot-tronik thermostats, this easy-to-remember thermostat product identification system will be used across the brands. Thermostats already available in the Behr Thermot-tronik product range are given a corresponding sales identifier. During the transition phase, thermostats can be ordered using the existing Behr Thermot-tronik number, which will be reassigned with the new MAHLE Aftermarket number upon receipt of the order.