Audi A4

since 1994 of release

Repair and car operation

A4 Audi
+ Running gear
+ Regular servicing
+ Engines
+ Turbo-supercharging
+ exhaust System
- Cooling system
   So there is a cooling
   Check of level of cooling liquid
   Antifreeze check
   Check of system of cooling on tightness
   Locking cover of system of cooling
   The help at malfunctions
   Water pump
   Maple belt of the water pump
   Various models of fans
   Vyazkostny 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 absorption channels
+ injection System
+ Coupling
+ Transmission and main transfer
+ Suspension bracket of wheels and steering
+ Brakes
+ Wheels and tires
+ Electrotechnical equipment
+ ignition System
+ Lighting
+ Alarm equipment
+ Tools and devices
+ Heating and ventilation
+ body Details
+ Salon
Search of malfunctions
Technical characteristics

Locking cover of system of cooling

In system of circulation of cooling liquid under pressure the locking cover on a broad tank plays 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 system of cooling exceeds 1,2–1,5 bar, the valve of adjustment of an elevated pressure opens. Leveling pressure, can leave a little water vapor.
  • When cooling liquid is again compressed, and in system of cooling there is a lowered pressure. For alignment of the lowered pressure in a cover there is the second valve. It opens at the lowered pressure in 0,06-0,1 bar, and atmospheric air can get into a broad tank.

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

The one who does not want to spend effort to check, can simply replace rather inexpensive cover. In a workshop it check a manometer:


  1. Pump up pressure.
  2. At pressure 1,2–1,5 bar the valve should open.
  3. At the removed cover compress 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 again is approximated, the valve as it should be.
  7. If in the mornings before the first start-up hoses of supply of cooling liquid are flattened, for certain not as it should be the valve of the lowered pressure.