Warning! Replacing the A/C refrigeration line hoses should be left to a professional workshop with the necessary equipment and qualifications to safely discharge the system. Never disconnect any refrigeration lines until the system has been completely discharged!
General information
Under the influence of high temperatures that occur in the engine compartment of a car, the material of the rubber and plastic hoses laid inside it begins to deteriorate over time. All hoses located under the hood should be regularly inspected for cracks, signs of leaks, signs of hardening of the material and weakening of the nipple connections.
Detailed information on checking the condition of the engine cooling and interior heating system hoses is provided in Section Checking the condition of the cooling system components.
Some, but not all, hoses use clamps to secure them to their fittings. Check that the hose clamps are tightly tightened - loosening them will cause leaks. If the hose is mounted to a fitting without a clamp, make sure that its end remains flexible enough to form a tight seal against the fitting surface.
Vacuum hoses
Typically, all vacuum hoses, especially those used in emission control systems, are color-coded or have colored stripes molded into their walls. Different systems may have different requirements for the wall thickness of the vacuum hoses used in them. Hoses must provide different resistance to collapse, temperature effects, and other factors. Make sure that replacement hoses match the parameters of those removed from the vehicle.
Usually, the only way to reliably assess the condition of a vacuum hose is to remove it from the vehicle. If you have to remove more than one hose, make sure to clearly mark them first so that they are connected correctly during assembly.
When checking the vacuum hose, do not forget to also assess the condition of its plastic nipple connections - inspect the nipple for cracks and make sure the hose fits tightly on it. When pulled onto the nipple, the hose should not deform unevenly, causing vacuum losses.
A short piece of vacuum hose with an internal diameter of about 7 mm is an excellent stethoscope, with which sources of vacuum losses are quite easily identified. One end of the hose is pressed to the surface being checked, the other to the ear. Vacuum losses are always accompanied by a hissing sound. Caution: When listening to components, try not to touch such moving components inside the engine compartment as drive belts, fan blades, etc.!
Fuel hoses
Warning! When servicing fuel system components, remember that gasoline is a highly flammable liquid. Do not smoke near the work area, do not approach it with an open flame! Immediately collect all traces of spilled fuel, put the rags soaked in fuel and lubricants in a place where there is absolutely no chance of its accidental ignition! Always keep a class B fire extinguisher at hand! Try to avoid gasoline coming into contact with exposed areas of skin - prolonged contact of this kind can lead to the development of cancer. Remember that the fuel injection system tract is constantly under excess internal pressure, which must be released before starting work (see Chapter Power and exhaust systems).
Inspect all rubber fuel hoses for signs of material aging and other defects. Pay particular attention to the condition of kinks and areas immediately before the ends are pushed onto the fittings.
Only high-quality fuel hoses should be used as replacement lines. Under no circumstances should non-reinforced vacuum hoses, transparent plastic tubes or garden hoses be installed in the fuel system tract. Spring-type clamps are usually used to secure fuel hoses to the fittings. Such clamps lose their strength over time, and often unexpectedly jump off when the hose is disconnected. It would be wise to replace such clamps with more reliable and safe worm or screw clamps.
Metallic lines
Sections of metal tubing are often used as fuel lines. Carefully inspect all rigid fuel lines for dents, kinks, or other deformations. Make sure there are no cracks or signs of cracking.
If any section of the metal line is to be replaced, use only seamless steel tubing as a replacement. Copper and aluminum tubing are not suitable for use as replacements because they do not provide adequate resistance to the vibrations generated in the system during engine operation.
Carefully inspect the metal brake pipes where they connect to the master cylinder and the limiter valve (if provided). Pay attention to defects such as cracks, try to identify signs of loosening of the fasteners. If traces of leaks are detected, it is necessary to immediately check the condition of the entire brake system as a whole.