A4 Audi
+ Running gear
+ Regular servicing
+ Engines
+ Turbo-supercharging
+ System of an exhaust
- Cooling system
So there is a cooling
Check of level of cooling liquid
Antifreeze check
Check of the cooling system on tightness
Radiator
Locking cover of the cooling system
Thermostat
The help at malfunctions
Water pump
Maple belt of the water pump
Various models of fans
Viscous fan
The radiator fan with the electric drive
Violations in operation of the fan of a radiator
The help at malfunctions
+ Fuel tank and fuel pump
+ Air filter and channels of absorption
+ System of injection
+ Coupling
+ Transmission and main transfer
+ Suspension bracket of wheels and steering
+ Brakes
+ Wheels and tires
+ Electrotechnical equipment
+ System of ignition
+ Lighting
+ Alarm equipment
+ Tools and devices
+ Heating and ventilation
+ body Details
+ Salon
Search of malfunctions
Technical characteristics
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The help at malfunctions
Thermostat
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Signs
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Reasons/consequences
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A. Temperature rises slowly, operational temperature is reached later, insufficient effect on -
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The valvate plate of the thermostat is blocked in the provision "openly" (German of "Offen") (for example, because of a deposit); the liquid stream to a radiator is constantly open. The engine too long works in not heated-up state. But for the small period of time it does not do harm. Despite it, change the thermostat somewhat quicker. |
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B. The arrow of the indicator of temperature is rejected to a limit, despite the correct level of cooling liquid to the right, the control bulb of cooling liquid blinks. The radiator and the lower hose going to a radiator, cold. |
The valvate plate of the thermostat is blocked in situation "Geschlossen" "is closed" (German) (for example, because of a defective or not tight box of the thermostat). Do not continue a trip at all, differently there will be heavy thermal damages of the engine! At once replace the thermostat. |
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Council: If on the way the engine begins to boil because of the defective thermostat, only towage or full dismantle of the thermostat on a place will help. If you made the decision to dismantle the thermostat, in the beginning have to wait, temperature of cooling liquid will not go down yet. |
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Four-cylinder engine: here the internal device of the water pump and the thermostat is shown (in a section). The bladed wheel (1) water pump is well visible. Nearby there is a thermostat (2). |
On the right: at the six-cylinder engine the case of the thermostat (shooter) is on the right ahead at the engine block.
At the left: in drawing assembly position of the thermostat at the four-cylinder engine is shown. The air valve (shooter) has to be turned up.
Dismantle of the thermostat
It is very difficult to dismantle the jammed thermostat on the way. It is located quite far below therefore it is necessary to merge almost all cooling liquid. Besides at the hot engine will pass a lot of time before you are able to begin work, without being afraid thus to burn hands. At installation of the new thermostat it is necessary to replace also sealing ring on the case of the thermostat and the water pump.
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- For all models: completely merge cooling liquid.
- Four-cylinder engine: dismantle the lower facing of a motive compartment (the head Detali of a body).
- Unscrew below on the case of the water pump a hose (that already became for plum of cooling liquid).
- Unscrew two bolts below on a thermostat case cover.
- Remove a cover and the thermostat.
- Six-cylinder engine: take off maple a belt, dismantle the tension device.
- Dismantle a cover of a gear belt (head Dvigateli). The gear belt remains on a place.
- Dismantle a hose of supply of cooling liquid to a radiator below on a branch pipe for a hose on the thermostat case.
- Unscrew two bolts on a thermostat case cover.
- Carefully lift a gear belt over a thermostat case crossing point, remove the case.
- Take out the thermostat.
- For all models: at installation of the new thermostat its small sealing plate has to be turned to the engine.
- Only for six-cylinder engine: the air valve in an external ring of the thermostat has to be turned up.
- Replace a sealing ring.
- Tighten bolts on the case of the thermostat and the water pump with the moment of an inhaling of 10 Nanometers.
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Check of the thermostat
By means of the built-in thermometer you can check, whether the thermostat opens at the set temperature.
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Beginning of opening
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End of opening
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Min. course of opening
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About 87 °C
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About 102 °C
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About 8 min.
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- Dismantle the thermostat.
- Suspend the thermostat in capacity with water and warm water.
- Check, whether the valvate plate in a saddle at achievement of temperature of 87 °C rises.
- At this check the end of opening can be reached not completely (as it is known, water in open capacity boils approximately at 100 °C), but nevertheless it is visible, whether the thermostat opens more strongly.
- But the total length of the course of opening is almost reached. But that is visible, is already enough to define the defective thermostat.
- At the slightest doubt in serviceability of the thermostat replace it.
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