Audi A4

since 1994 release

Manual of the car

Audi A4
+ 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
   Locking cover of the cooling system
   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


Locking cover of the cooling system

In system of circulation of cooling liquid under pressure the locking cover on a broad tank plays an important role:

  • The sealing surface of the screwed-up cover strong nestles on edge of an opening of a broad tank. Pressure cannot go down.
  • If when heating pressure in the cooling system exceeds 1,2–1,5 bars, the valve of adjustment of elevated pressure opens. Leveling pressure, will be able to leave a little water vapor.
  • When cooling liquid compresses again, and in the cooling system there is a lowered pressure. For alignment of the lowered pressure in a cover there is the second valve. It opens with the lowered pressure in 0,06-0,1 bars, and atmospheric air can get into a broad tank.

Check of valves of the increased and lowered pressure make-shifts

The one who does not want to waste efforts to check can just replace rather inexpensive cover. In a workshop it is checked the manometer:


  1. Pump up pressure.
  2. With a pressure of 1,2-1,5 bars the valve has to open.
  3. At uncovered squeeze a thick hose of supply of liquid.
  4. Put on and screw up a cover, release a hose.
  5. Release a hose.
  6. If the compressed hose is rounded again, the valve as it should be.
  7. If in the mornings before the first start-up hoses of supply of cooling liquid are flattened, then for certain not as it should be the valve of the lowered pressure.