Caution: Replacement of the air conditioning refrigeration hoses must be performed at a service station or workshop equipped to safely relieve pressure in this system. Never disconnect the refrigeration hoses or remove its components without first relieving the pressure.
General information
1. Exposure to high temperatures in the engine compartment will gradually deteriorate 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.
2. Information regarding cooling system hoses is given in Section 4 and information regarding brake system hoses is given in Section 8.
3. Most (but not all) hoses are secured with clamps. Where clamps are used, check that they are securely tightened to prevent leaks. If clamps are not used, check that the hose is not swollen and/or hardened where it connects to the fitting.
4. If there are signs of a fluid leak, but the type or origin of the fluid cannot be identified, leave the car for a long time and place a large piece of paper or rag under it. This will help to find the location of the fluid leak, as well as identify it by color.
Note: Some leaks may only become apparent when the engine is running.
Vacuum hoses
5. Vacuum hoses, especially those used in emission control systems, are usually color-coded or have colored stripe inserts. Different systems require hoses with different wall thicknesses, heat resistance, and resistance to collapse. When replacing hoses, make sure the material of the new hose matches the material of the old one.
6. Often the only reliable way to check the condition of a hose is to remove it completely from the vehicle. When removing several hoses at a time, mark their ends and fittings to ensure proper reassembly.
7. When checking the vacuum hoses, be sure to also check the plastic T-joints. Inspect them for cracks that could cause leaks.
8. A leak in the vacuum hose means that air is being sucked into the hose (but it doesn't come out of the hose), and this makes the leak difficult to detect. To detect vacuum leaks, you can use a short piece of vacuum hose as a stethoscope. When the end of the hose is directly over the leak, a hissing sound will be clearly audible through it. Listen to all vacuum hoses and connections for the characteristic hissing sound that indicates a leak.
Caution: When using this type of stethoscope, be careful not to allow your body to come into contact with moving components in the engine compartment, such as drive belts, cooling fan, etc.
Fuel hoses
Caution: When inspecting or servicing fuel system components, certain precautions must be taken. Perform all work in a well-ventilated area and keep away from open flames (for example, lit cigarettes) or unprotected lamp shades to the work site. Immediately collect spilled fuel with rags, which are then placed in a place where it cannot ignite. If fuel gets on your skin, wash it off immediately with plenty of water and soap. When working with the fuel system, wear safety glasses and always have a fire extinguisher at hand.
9. Fuel hoses are usually under pressure, so be prepared to collect any squirting fuel when disconnecting them.
Note: On gasoline vehicles equipped with fuel injection, before servicing the fuel hoses, relieve the pressure in the system by starting the engine with the fuel pump disconnected and allowing the engine to run until it stalls. On diesel models, do not allow the injection pump to run dry (without fuel).
10. Check all rubber fuel hoses for signs of wear and tear. Pay particular attention to bends and in front of fittings, such as where the hose connects to the fuel pump or filter, where cracks may form.
11. Use only high quality fuel hoses. Never use non-reinforced vacuum hoses, clear plastic tubes or water hoses as fuel hoses.
12. Band-type clamps are commonly used to secure fuel hoses. These clamps will weaken over time and may "pop out" when removed. When replacing hoses, replace these clamps with screw-type clamps.
13. Minor fuel leaks are difficult to pinpoint because fuel tends to evaporate quickly once it comes into contact with air, especially in a hot engine compartment. Small droplets may disappear before the leak can be located. Metal fittings contract as they cool, and rubber hoses will be loosened, so potential leaks will be more obvious as the engine warms up when starting from cold.
Metallic lines
14. There are sections of metal tubing installed between the fuel pump and the fuel injection system and these should be carefully checked for dents, twists or cracks.
15. If a section of metal line needs to be replaced, use only seamless steel tubing as copper and aluminum tubing are not strong enough to withstand vibrations caused by engine operation.
16. Check metal brake lines where they connect to the master cylinder, pressure regulator/ABS hydraulic modulator for cracks or loose nipple connections. Any signs of brake fluid leakage require immediate and thorough inspection of the entire brake system.