Mercedes C-Class

1. Before removing and checking operability of the thermostat, be convinced that problems with cooling of the engine arose not owing to insufficient amount of cooling liquid or a weak tension of a driving belt. Be convinced of serviceability of the indicator located on a control panel.
2. If you noticed that the engine long gets warm to working temperature (according to indicator indications), the thermostat, possibly, is jammed in open situation. In this case it is necessary to replace the thermostat.
3. On the other hand, long warming up can be a consequence of lack of the thermostat. It could make specially or inadvertently (forgot to establish after repair). Do not use the car without the thermostat. The control system of the engine will keep the engine in a warming up mode longer time. During this time the engine will consume bigger amount of fuel, and the fulfilled gases will contain bigger amount of harmful impurity.
4. If the engine overheats, touch the top hose of a radiator. If it not hot, but the engine перегрет, the thermostat, probably, jammed in a closed position. Liquid does not get to a radiator and circulates on a small circle. In this case replace the thermostat.
5. If the top hose of a radiator hot, it means that the thermostat is open and liquid normally circulates on system. In this case familiarize with the recommendations provided in the section «Diagnostics of malfunctions» of Introduction.

1. Remove the thermostat case.

2. Check position of the thermostat through a connecting branch pipe in the case. Measure the size "a" on the thermostat.

3. If the thermostat at room temperature is abroach — it is faulty and is subject to replacement.
4. For rough check of operability of the thermostat suspend its case on a piece of a twine in a vessel with water. The case of the thermostat should not concern vessel walls. Start to heat up a vessel.
5. In process of water heating the thermostat should open (it occurs directly ahead of water boiling). As the temperature of boiling of water 100°С, the thermostat can not open completely (address to Specifications). Take the thermostat and let's to it cool down. In process of cooling it should be closed completely.
6. If the thermostat does not open when heating or is not closed when cooling, replace it.
7. At installation of the thermostat keep in mind the following:

a) Carefully clear interfaced surfaces and replace a sealing ring.
b) Place the thermostat in a casing, it is correct сориентировав.
c) Tighten bolts of fastening of a cover, having made demanded effort.
d) Establish all hoses on former places then fill in cooling liquid (address to Head Routine maintenance).
e) Start the engine, warm up to working temperature and be convinced of absence of leaks.