Attention! Replacing air conditioning hoses (K/V) should be carried out in a workshop or workshop with equipment to safely relieve pressure in this system. Never disconnect hoses of the K/V system and do not remove its components without first relieving pressure.
General information
Exposure to high temperatures in the engine compartment leads to the gradual failure of the rubber and plastic hoses used in various systems. Hoses should be checked regularly for cracks, loose clamps, hardening of materials, and signs of leaks.
For information related to cooling system hoses, see Section Checking fluid levels, leak control, and to the hoses of the brake system - in Section Checking the Condition of Suspension and Steering Components.
Most hoses (But not all) fastened with clamps. Where clamps are used, check that they are securely tightened to ensure there are no leaks. If clamps are not used, make sure that the hose at the fitting does not swell and/or harden.
If there are signs of any fluid leaking, but the type or origin of the fluid cannot be recognized, leave the vehicle for a long time and place a large piece of paper or rag under it. This will help to find the place where the liquid is leaking, as well as identify it by color. But keep in mind that some leaks may only show up when the engine is running.
Vacuum hoses
Usually vacuum hoses, especially those used in the emission control system (EGR), are color-coded or have colored stripe inserts. Different systems require the use of hoses with different wall thicknesses, heat resistance and different collapse resistance. When replacing hoses, make sure that the material of the new hose matches the material of the old one.
Often the only reliable way to check the condition of a hose is to completely remove it from the vehicle. When removing multiple hoses at the same time, mark their ends and fittings to ensure correct assembly.
When checking the vacuum hoses, be sure to also check the T-shaped plastic connections. Inspect them for cracks that could cause leaks.
A leak in the vacuum hose means that air is being sucked into the hose (does not come out of the hose), and this makes the leak difficult to detect. You can use a small piece of vacuum hose as a stethoscope to check for vacuum leaks. When the end of the hose is directly above the leak, a hissing sound will be clearly audible through it. Listen to all vacuum hoses and connections for a characteristic hiss that indicates a leak.
Attention! When using this stethoscope, be careful not to come into contact with moving parts in the engine compartment, such as the drive belt, cooling fan, etc.
Fuel hoses
Attention! Certain safety precautions must be observed when inspecting or servicing fuel system components. Perform all work in a well-ventilated area, keep open flames away (e.g. lit cigarettes) or unprotected lampshade lamps to the place of work. Spilled fuel should be immediately collected with rags, which should then be put in a place where it cannot be ignited. If fuel comes into contact with skin, wash immediately with plenty of soap and water. When working on the fuel system, wear safety goggles and always have a fire extinguisher handy.
Fuel hoses are usually pressurized, so be prepared to collect splattered fuel when disconnecting them.
Note. On vehicles equipped with a fuel injection system, the pressure in the system must be relieved before servicing the fuel hoses (see Section Depressurizing the supply system).
Check all rubber fuel hoses for signs of wear and tear. Pay special attention to bends and in front of fittings, for example, the connection between the hose and the fuel pump or filter, where cracks can form.
Use only high quality fuel hoses. Never use non-reinforced vacuum hoses, clear plastic tubes or water hoses as fuel.
Band-type clamps are commonly used to secure fuel hoses. These clamps loosen over time and may «jump out» upon removal. When replacing hoses, replace these clamps with screw-type clamps.
Insignificant fuel leaks are difficult to accurately determine, because. fuel tends to evaporate quickly as soon as it comes into contact with air, especially in a hot engine compartment. Small drops may disappear before the leak can be located. The metal fittings shrink when cooled and the rubber hoses will loosen up so that potential leaks will be more obvious while the engine is warming up on a cold start.
Metal lines
Sections of metal tubes are installed between the fuel pump and the fuel injection system, which should be carefully checked for dents, twists or cracks.
If a section of metal line needs to be replaced, use only seamless steel tubing as the copper and aluminum tubes are not strong enough to withstand the vibrations caused by the engine.
Check the metal brake lines where they connect to the GTZ, pressure regulator/ABS activator for cracks or loose fittings. Any sign of a brake fluid leak requires an immediate overhaul of the entire brake system.