Audi A4

Since 1994 of release

Repair and car operation

Audi А4
+ Running gear
+ Regular servicing
+ Engines
+ Turbo-supercharging
+ Exhaust system
- Cooling system
   So there is a cooling
   Check of level of a cooling liquid
   Antifreeze check
   Check of system of cooling on tightness
   Zapornaja cover of system of cooling
   The thermostat
   The help at malfunctions
   The water pump
   Klinovoj belt of the water pump
   Various models of fans
   The vjazkostnyj fan
   The fan of a radiator with the electric drive
   Infringements in work of the fan of a radiator
   The help at malfunctions
+ Fuel tank and the fuel pump
+ The air filter and channels всасывания
+ Injection system
+ Coupling
+ Transmission and the main transfer
+ Suspension bracket of wheels and steering
+ Brakes
+ Wheels and tyres
+ The electrotechnical equipment
+ Ignition system
+ Illumination
+ The alarm equipment
+ Tools and devices
+ Heating and ventilation
+ Body details
+ Salon
Search of malfunctions
Technical characteristics

The help at malfunctions

The thermostat

The reason/consequence
A.Temperatura rises slowly, the operational temperature is reached later, insufficient effect on -
The klapannaja plate of the thermostat is blocked in position "openly" (it. Оffen) (for example, because of a deposit); the liquid stream to a radiator is constantly opened. The engine too long works in not heated-up condition. But for the small period of time it does not put harm. Despite it, change the thermostat somewhat quicker.
B. The arrow of the indicator of temperature is rejected to the right to a limit, despite correct level of a cooling liquid, the control bulb of a cooling liquid blinks. A radiator and the bottom hose going to a radiator, cold.  The klapannaja plate of the thermostat is blocked in position "is closed" (it. Geschlossen) (for example, because of a defective or not tight box of the thermostat). At all do not continue a trip, differently there will be heavy thermal damages of the engine! At once replace the thermostat.

 Council: If on the journey the engine begins to boil because of the defective thermostat, towage or full dismantle of the thermostat on a place will help only. If you have made decision to dismantle the thermostat in the beginning should wait, the temperature of a cooling liquid will not go down yet.

The four-cylinder engine: here the internal device of the water pump and the thermostat (in a cut) is shown. It is well visible лопастное a wheel (1) water pumps. Nearby there is a thermostat (2).

On the right: at the six-cylinder engine the case of the thermostat (marksman) is on the right ahead at the engine block.

At the left: in drawing assembly position of the thermostat is shown at the four-cylinder engine. The air valve (arrow) should be turned upwards.

Thermostat dismantle

The jammed thermostat is very difficult for dismantling on the journey. It is located far enough below, therefore it is necessary to merge almost all cooling liquid. Besides at the hot engine will pass a lot of time before you can begin work, without being afraid thus to burn hands. At installation of the new thermostat it is necessary to replace also a sealing ring on the case of the thermostat and the water pump.


  1. For all models: completely merge cooling liquid.
  2. The four-cylinder engine: dismantle the bottom facing of an impellent compartment (the head of the Detail of a body).
  3. Unscrew below on the case of the water pump a hose (that already became for plum of a cooling liquid).
  4. Unscrew two bolts below on a cover of the case of the thermostat.
  5. Uncover also the thermostat.
  6. The six-cylinder engine: remove клиновой a belt, dismantle the tension device.
  7. Dismantle a cover of a gear belt (the head Engines). The gear belt remains on a place.
  8. Dismantle a hose of giving of a cooling liquid to a radiator below on a branch pipe for a hose on the thermostat case.
  9. Unscrew two bolts on a cover of the case of the thermostat.
  10. Cautiously lift a gear belt over a crosspiece of the case of the thermostat, remove the case.
  11. Take out the thermostat.
  12. For all models: at installation of the new thermostat its small sealing plate should be turned to the engine.
  13. Only for the six-cylinder engine: the air valve in an external ring of the thermostat should be turned upwards.
  14. Replace a sealing ring.
  15. Tighten bolts on the case of the thermostat and the water pump with the moment of an inhaling of 10 Nanometers.

Thermostat check

By means of the built in thermometer you can check, whether the thermostat opens at the set temperature.

The opening beginning
The opening end
Minute an opening course
Nearby 87 С
Nearby 102 С
About 8 mines


  1. Dismantle the thermostat.
  2. Suspend the thermostat in capacity with water and warm up water.
  3. Check up, whether the plate in a saddle rises клапанная at achievement of temperature 87 С.
  4. At this check the opening end can be reached not completely (as it is known, water in open capacity boils approximately at 100 С), but nevertheless it is visible, whether the thermostat opens more strongly.
  5. But the total length of a course of opening is almost reached. But that it is visible to define the defective thermostat, already enough.
  6. At the slightest doubt in serviceability of the thermostat replace it.