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In order to examine the cooling system thermostat out of a service station open the bonnet and start the engine. Wait for about two minutes, and then touch the pipe, going from the thermostat to the radiator. It should be cold, as coolant at insufficiently warmed up engine moves through small circuit. If the pipe is hot, this means that the thermostat valve is not fit tightly to the mounting seat. Wait till the engine reaches operating temperature and touch the pipe again. It should be hot. The cool pipe point at jamming of the thermostat valve. For more detailed diagnostics, the component should be demounted, and for this you need to apply to specialists.

Most of all, necessity of component diagnostics is indicated by the following signs:

• activation of the engine overheating indicator on the dashboard;
• excessively long heating of the engine to its working temperature;
• increasing of fuel consumption;
• leakage of coolant near the component housing or streaks on its body.

You can replace the coolant thermostat on your own only in case if there is no need to demount auxiliary units for gaining access to it. For installation of a frameless thermostat, usually, you need to just drain coolant from the cooling system, demount the thermostat cap, remove the defective insert and install a new one into its place. During replacement of the thermostat with a housing you need to loosen pipes clamps, disconnect them from the component body, unscrew fasteners and then demount the whole unit. Install an operative thermostat into its place, connect the hoses back and fill coolant into the system. In some cars the thermostat is mounted into the cylinder head. In this case, for its replacement you will need to remove the timing belt and auxiliary units, and after this mandatory synchronization of the crankshaft and camshaft is performed. Performing of these works should be entrusted to professionals.

The thermostat is a device for adjustment of the power and direction of coolant flow. It is organized as follows: inside of the body there is a sensitive element, which is the main operating component of the part. Usually, it consists of a chamber, filled with wax and a rod, connected to the chamber. Operating principle of the thermostat lies in the following: when the engine and coolant get overheated, wax expands and drives the rod, which opens the valve for a required angle. Coolant starts moving through the big circuit, coming from the engine to the radiator, where its cooling is performed. Use of the thermostat helps to reach optimal temperature of the power unit at all its operational modes.

According to construction of the cooling system thermostats with and without housing can be used in the cars. Opening temperature of the component valve may be different in various cars, which should be taken into account during selection of the part.

It is better to install into your car the thermostats of well-known manufacturers such as Gates, Denso, Delphi, Stark Professional Line, Wahler, Ashika, Blue Print, Behr, Calorstat, Facet, Hella, Japanparts, Magneti Marelli, Mapco, Mahle, Nipparts, Triscan, Vemo. Their production is notable for efficiency and durability, and production range covers the most popular car models in Europe. In the assortment of these manufacturers you can find regular thermostats, opening degree of which is regulated by influence of coolant temperature only, as well as thermostats with electronic control, in a heating element of which a special resistor is built in. Thanks to the latter, the thermostat valve will open before the moment, when the engine reaches certain temperature, due to which the most efficient cooling of the engine is performed even in a high loads mode.

Also special and multi-purpose thermostats are presented on the aftermarket. The special ones are produced in accordance with peculiarities of the exact car model, that is why they will surely fit your car and will provide maximum operation efficiency of its cooling system. The multi-purpose ones have smaller price and may be installed into various vehicle models.