When a engine starts to overheat or can not reach operating temperature, it is most likely due to a fault in the cooling system. In addition to the water pump, the cooler and the fan, the thermostat plays a central role. Even the slightest malfunction of the thermostat - eg. due to corrosion – effects the engine performance immediately.
Corrosion occurs, among other things if a wrong coolant is used. The corrosion attacks the thermostats aluminum parts that almost "etch away" (see figures 1 and 2). But also mixing of different coolants can cause corrosion. Therefore avoid mixing different types of coolant together.
MAP controlled thermostat with clear signs of corrosion (Photo credit: Mahle)
Thermostat with coolant / additive not approved by the manufacturer. This has led to that the aluminum is "etched" away (Photo credit: Mahle)
Also, be sure to use only coolant approved by the car manufacturer and be aware of using the correct mixing ratio of coolant to water. Some car manufacturers prescribe that only distilled water and not tap water is added, as it may also have a negative effect due to its content of minerals - including limescale. We always think you should avoid the use of tap water.
Also check that the ground cable between the engine and body of the car is properly mounted and intact (figure 3) - thereby compensating for the occurrence of static electricity between the fuel supply system and the car body. A defective earth cable or a bad connection can speed up the damage due to electrolysis.
You should check that the ground cable is intact and properly connected (Photo credit: Mahle)
Coolant loses its corrosion-preventing ability over time, and therefore replacement of the coolant is part of the regular service inspection. It is recommended to replace the coolant every two years. Be sure to always follow the manufacturer's recommendations.