Audi 80/Avant (B4)

since 1991-1995 of release

Repair and car operation

Audi 80/Avant
+ Technical specification
+ Engines
+ System of production of the fulfilled gases
- Cooling system
   Check of level of cooling liquid
   Frost resistance check
   Check of system of cooling on tightness
   Carving cover of a broad tank
   List of malfunctions
   Water pump
   Maple belt of the water pump
   Fan of system of cooling
   Malfunctions of the fan of system of cooling
   List of malfunctions
+ Fuel tank and fuel pump
+ Air filter and airintaking channels
+ injection System
+ Coupling
+ Transmission and transmission
+ Suspension bracket and steering
+ Brake system
+ Anti-blocking system of brakes
+ Wheels and tires
+ Body electrosystem
+ ignition System
+ Lighting
+ Signalling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ body Elements
+ Search of malfunctions
+ Specifications

Carving cover of a broad tank

In the conditions of an elevated pressure of system of cooling the important role is played by a carving cover of a broad tank:

  • At the closed cover its sealing surface strong nestles on edge of an opening of a broad tank and if the safety valve is closed, losses of pressure are not present.
  • If when heating pressure in system of cooling exceeds 1,2 – 1,5 bar – the safety valve opens and a quantity of water vapor jumps out. Pressure is leveled.
  • When cooling liquid again decreases in volume, and in system of cooling the lowered pressure is formed. For an equilibration of this lowered pressure in a cover there is the second valve. It opens at the lowered pressure 0,06 – 1,0 bar so the system can include external air.

Check of a safety valve

Who does not want to suffer with check, in a suspicious case simply should replace rather inexpensive carving cover.

The workshop checks it by means of a manometer:

At pressure 1,2 – 1,5 bar the valve should open.

Check of the vacuum valve

It is possible to define approximately only, whether this valve works.


  1. At the removed carving cover strongly to squeeze a thick tube of system of cooling.
  2. To put on and tighten a cover.
  3. To release a hose.
  4. If the compressed hose again is approximated, the valve, most likely, as it should be.
  5. If tubes of system of cooling before the first start look in the morning flat and squeezed, the vacuum valve is for certain faulty.