Audi A4

Since 1994 of release

Repair and car operation

The water pump at the working engine constantly drives cooling liquid through numerous channels of cooling of the engine and thus takes away the warmth arising at the expense of combustion in cylinders. The pump accelerates a stream of a cooling liquid with the help лопастного a wheel which is at it on an underside.

The drive of the water pump in the four-cylinder engine is provided клиновым with a belt, in the six-cylinder engine – a gear belt. What way the cooling liquid flows on uncountable hoses and channels, depends on its temperature at present.

• If the engine is yet heated-up, the cooling liquid moves on a small contour which goes through the engine and the heating heat exchanger. Depending on engine model the oil radiator in addition is connected to a small contour of circulation of a cooling liquid.
• At temperature from above 87 С the thermostat opens the big contour in which the radiator is connected.
• If the temperature continues to raise further so, what even in a radiator environment reaches 82 С, вязкостное coupling of the fan of a radiator is switched to a rigid direct drive – the fan too rotates.
• In cars with an electric drive of the fan of a radiator (climatic installation) the fan if in a radiator the temperature reaches approximately 92 С is connected.

System of cooling of an elevated pressure

At working temperature in cooling system there is an elevated pressure in 1,2–1,5 bar that considerably raises temperature of boiling of water – over 100 С under usual conditions. Thus the reserve is created, the engine can reach working temperatures from above 100 С, and thus there is no danger of boiling of a liquid in cooling system.

Correct pressure in cooling system is provided запорной with a cover of a broad tank in which are an elevated pressure safety valve (nearby 1,2–1,5 bar) and a safety valve of the lowered pressure (0,06–0,1 bar).

The valve of the lowered pressure lets in air stream if the temperature of a cooling liquid goes down and, hence, occupies smaller volume.