Attention! A/C hose replacement should be performed by a dealer or automotive air conditioner specialists who have the appropriate equipment to handle the system safely. Never remove the A/C components or hoses until you have relieved the refrigerant from the system, which should also be done by your dealer or vehicle air conditioner technician.
General information
1. High temperatures in the engine compartment can cause deterioration of the rubber and plastic hoses used to run the engine, accessories and emission control systems. Periodic checks should be made for cracks, loose clamps, material hardening and leaks.
2. Specific information for coolant hoses can be found in paragraph 11.
3. Some, but not all, hoses are secured to the fittings with clamps. Where clamps are used, make sure they are tight, as insufficient torque may result in leakage at the hose connection. If clamps are not used, make sure that the hose has not expanded and/or hardened where it sits on the nozzle, as this may cause a leak.
Vacuum hoses
4. Vacuum hoses, especially those used in emission control systems, are characterized by the use of color coding or embossed colored identification bands. Different systems require hoses with different wall thicknesses, collapse resistance and heat resistance. When replacing hoses, make sure the new hoses are of the same material.
5. Often the only way to test a hose is to remove it completely from the vehicle. If you are removing multiple hoses, mark them and their associated fittings to ensure correct installation.
6. When checking vacuum hoses, be sure to check all plastic T-fittings (tees). Inspect the fittings for cracks and the hose end seats for deformation, as these defects can cause leakage.
7. A small piece of vacuum hose can be used as a stethoscope to detect vacuum leaks (with an inner diameter of approx. 6 mm). Place one end of the hose to your ear and, using the other end as a probe, inspect the hoses and connections, listening for «hissing sound», which is a sign «vacuum leaks».
Attention! When examining a vacuum hose with a stethoscope (improvised or real) be very careful not to hit moving engine parts such as drive belts, cooling fan, etc.
Fuel hoses
Attention! Gasoline is highly flammable, so extra precautions must be taken when working on any part of the fuel system. Do not smoke or allow open flames or unprotected light fixtures near the work area. Do not work in rooms where there are devices that work on the (e.g. water heaters or clothes dryers). Since gasoline is a carcinogen, do not allow fuel to get into open areas of the body, work with gloves that are resistant to its effects. In case of contact with fuel on the skin, the affected area should be washed immediately with soap and water. Wipe up spilled fuel immediately and do not store fuel-soaked rags where they could ignite. The fuel system is under constant pressure, so be sure to depressurize the fuel system first before disconnecting the fuel lines. Wear safety goggles when doing any work on the fuel system. Keep a Class B fire extinguisher handy at all times.
8. Check all rubber fuel lines for deterioration and chafing. Check them especially carefully for cracks in the bends and immediately in front of the fittings, for example, where the hose connects to the fuel filter.
9. When replacing the fuel line, use a high quality fuel line. Under no circumstances should an unreinforced vacuum line, clear plastic line or water hose be used as the fuel line.
10. Normally, spring loaded clamps are used on the fuel lines. These clamps often lose tension over time and can spring back when removed. At each hose change, replace all spring loaded clamps with worm gear clamps (screw) clamp.
Metal lines
11. Metal pipes are often used as fuel lines between the fuel pump and the fuel rail. Carefully check the fuel line for deformation, flattening and cracking.
12. If the metal fuel line must be replaced, only seamless in-line piping should be used, as copper or aluminum piping does not have the strength needed to withstand normal engine vibration.
13. Check the metal brake lines at the connections to the master cylinder and pressure regulator (in the presence of) for cracks or blinding tightening of connections. Any sign of a brake fluid leak requires an immediate full inspection of the brake system.