Audi A4, S4

since 2000 release

Repair and operation of the car

Check of a state and replacement of hoses of a motive compartment, localization of leaks

Replacement of hoses of the air conditioning system has to be made at car repair shop of representative office or in a specialized workshop where there is an equipment for safe dumping of pressure in system. Never disconnect hoses of system and do not remove its components, previously without having dumped pressure.

General information

Influence of high temperatures in a motive compartment leads to gradual failure of the rubber and plastic hoses used in various systems. It is necessary to make regularly check of hoses on existence of cracks, weakening of fastening of collars, hardening of materials and signs of leaks.

Information relating to cooling system hoses is given below, and to hoses of brake system - in the Section of Check of brake system. Adjustment of the parking brake.

The majority of hoses (but not all) fasten by means of collars. Where collars are used, check reliability of their fastening providing lack of leaks. If collars are not used, make sure that the hose in a junction with the union was not inflated and/or did not harden, allowing leaks.

If there are signs that there is a leak of any liquid, but you cannot distinguish type of liquid or an exact origin, it is necessary to leave the car for long time and to put a big piece of paper or a rag under the car. It will help to find a liquid course place, and also will help to identify liquid on color. But keep in mind that some leaks can be shown only at the working engine.

Vacuum hoses

Usually vacuum hoses which are especially applied in systems of decrease in toxicity of the fulfilled gases differ in color or have color strips.

Various systems demand use of hoses with various thickness of walls, thermal stability and various resistance to a collapse. When replacing hoses watch that material of a new hose corresponded to material of the old.

Often only reliable way of check of a condition of a hose is its full removal from the car. At removal more than one hose take care of accurate designation of hoses and unions to provide the correct assembly.

When checking vacuum hoses do not forget to check T-shaped plastic connections also. Examine them on existence of cracks which can cause leaks.

Using a similar stethoscope, be careful, do not allow contact with moving components in a motive compartment, such as a driving belt, the cooling fan, etc.)

Leak in a vacuum hose means that air is sucked in in a hose (but does not leave a hose), and it does leak very difficult for detection. For identification of leakages of vacuum it is possible to use a small piece of a vacuum hose as a stethoscope. When the end of a hose directly is over a leak place, the hissing sound will be clearly audible through a hose. Listen to all vacuum hoses and connections on existence of the characteristic hissing testifying to leak. It is necessary to avoid contact with hot and moving details as the engine when checking has to work.

Fuel hoses

Fuel hoses usually are under pressure therefore at their detachment be ready to that fuel will be sprayed and he needs to be collected.

Before serving fuel hoses, it is necessary to dump pressure in system of injection of fuel.

Check all rubber fuel hoses for existence of signs of wear and attritions. Pay special attention to sites of a bend and in front of unions, for example a hose junction with the fuel pump or the filter, cracks can be formed there.

Use only high-quality fuel hoses. Never, under no circumstances do not use as fuel not reinforced vacuum hoses, transparent plastic tubes or water hoses.

For fastening of fuel hoses collars of tape type are usually used. These collars weaken a tension over time and can "jump out" at removal. When replacing hoses replace such collars with collars of screw type.

Precisely it is difficultly to define leak of fuel until leak becomes essential and, therefore, easily visible. Fuel tends to evaporate quickly as soon as it contacts with air, especially in a hot motive compartment. Small drops can disappear before you are able to define a leak place. If you suspect that leak of fuel in the field of a motive compartment takes place, then cool the engine and start it, it cold, at an open cowl so far. Metal subjects contract when cooling, and rubber hoses tend to be weakened so any leaks will be more obvious while the engine heats up at start from a cold state.

Metal lines

Between the fuel pump and system of injection of fuel sections of metal tubes are often inserted. Carefully check these tubes for existence of dents, twisting or cracks.

If the section of the metal line needs to be replaced, use only seamless steel tubes since copper and aluminum tubes are insufficiently strong to resist to the vibrations caused by operation of the engine.

Check metal brake lines in places of their connection with the main cylinder and with the regulator of pressure or ABS (if it is available) on existence of cracks or the weakened nipple connections. Any signs of leak of brake fluid demand immediate careful survey of all brake system.

Hoses of system of hydrostrengthening of a wheel

Check hoses of system of hydrostrengthening of a wheel for existence of signs of leak of liquid, the weakened nipple connections and worn-out collars. The proceeding hoses and worn-out collars should be replaced.

Cooling system hoses

Leaks in the cooling system usually are found on white or colors of a rust to a raid in the area adjoining leak.

Carefully check a radiator and hoses of cooling liquid on inam, gaps and signs of aging. It is easier to find cracks if to press a hose. Pay special attention to collars which attach hoses to cooling system elements. Collars of fastening of a hose which were strongly tightened, can cause a gap or a puncture of a hose, leaks in the cooling system will be result of that. Examine all hoses and surfaces of connection of hoses regarding leaks. If any problems of similar character with leaks are found, replace this component or laying.