Valve device

A valve device, in particular for a cooling water system of a motor vehicle, with a housing comprising a first connection and a second connection for a first liquid circuit, and a third connection and a fourth connection for a second liquid circuit, wherein the first connection is permanently fluidically connected to the second connection, and with a valve unit comprising a movably mounted valve element with which a thermally activatable spring element is associated, and which opens a connection between the third connection and the fourth connection in a first end position and cuts off the connection in a second end position, wherein the thermally activatable spring element is arranged in a chamber located between the first connection and the second connection, which is permanently cut off from the third and the fourth connection and which preloads the valve element in the direction of the second end position, and in that the valve unit is designed as a plug-in module which can be plugged into the housing and comprises a cylindrical module housing comprising at one end a bottom with an opening, which delimits the chamber, wherein the valve element is slidably mounted in the module housing and led radially by means of a free end in a sealing/tight manner through the opening.