Genuine Mercedes-Benz C240 Thermostat

Mercedes-Benz C240 Thermostat Parts and Q&A

• Thermostat Housing
  112-203-02-75
  Q: What should you check before assuming the thermostat is responsible for a cooling system problem on Mercedes-Benz C240?

  A:

  Probably everyone knows by the time they reach adulthood that, before assuming something is wrong in a cooling system, the first step is to look at the amount of coolant in the system, the tightness of its drive-belt, or the operation of its temperature gauge or temperature light. When it takes a long time before the engine warms up, it is possible that the thermostat has become stuck open, and should be changed. When the engine is too hot to run, or overheats, the thermostat should also be extensively tested, which in turn cannot be done unless the thermostat is out of the car. When the thermostat will not close at room temperature, it is not functioning properly, and needs to be replaced; the interim economy and the emissions of driving cars and trucks without the thermostat can be detrimental. To test a thermostat, place it in a container of cold water together with a thermometer, warm the water and record the temperature at which the thermostat starts to open and when it is completely open and compare this to the specs. In case the thermostat is not opening and closing as per specifications or becomes stuck in any position it needs replacement. To replace: drain the engine coolant, take out the trim panel and coolant hose(s) in the cover of the thermostat housing, and unbolt the housing cover. Wipe down the surfaces, replace an O-ring, and reassemble everything in reverse, also refilling and bleeding the cooling system and inspecting for leaks and correct functionality. Other procedures to be followed correspond to the type of engine to be installed; e.g., before installation, hoses must be removed, all old gaskets and sealants cleaned and serpentine belt must be removed.