Inspection and replacement of engine compartment hoses, leak detection

GENERAL INFORMATION

CAUTION

Air conditioning system hoses must be replaced at a authorized dealer service station or a specialist workshop equipped to safely discharge the system pressure. Never disconnect system hoses or remove system components without first discharging the pressure.

PROCEDURE

1. Exposure to high temperatures in the engine compartment causes gradual deterioration of rubber and plastic hoses used in various systems. Regularly inspect hoses for cracks, loose clamps, hardening of materials, and signs of leaks.

2. For information on cooling system hoses, refer to the Cooling System Function Check subsection. For brake system hoses, refer to the Brake System Check subsection.

3. Most hoses (but not all) are secured with clamps. Where clamps are used, check that they are tight enough to prevent leaks. Where clamps are not used, make sure the hose at the fitting connection is not swollen and/or hardened, which can allow leaks.

4. If there are signs of fluid leakage but you cannot identify the fluid type or exact source, leave a large piece of paper or cloth under the vehicle overnight. This will help locate the leak and also help identify the fluid by its color. Keep in mind that some leaks may only appear with the engine running. Vacuum Hoses

5. Vacuum hoses, especially those used in emission control systems, are usually color-coded or marked with colored stripes.

Different systems require hoses with different wall thicknesses, heat resistance, and collapse resistance. When replacing hoses, make sure the new hose material matches the original.

6. Often the only reliable way to check hose condition is to remove the hose completely from the vehicle. When removing more than one hose, clearly label the hoses and fittings to ensure correct reassembly.

7. When inspecting vacuum hoses, also check the T-shaped plastic connectors. Inspect them for cracks that may cause leaks.

CAUTION

When using such a stethoscope, take care to avoid contact with moving components in the engine compartment, such as the drive belt, cooling fan, etc.)

8. A leak in a vacuum hose draws air into the hose (rather than letting it out), which makes the leak very difficult to detect. To locate vacuum leaks, use a short piece of vacuum hose as a stethoscope. When the end of the hose is positioned directly over the leak, a hissing sound will be clearly heard through the hose. Listen to all vacuum hoses and connections for a hissing sound that indicates a leak. Avoid contact with hot and moving parts, as the engine must be running during this check. Fuel Hoses

CAUTION

Observe certain precautions when inspecting or servicing fuel system components. Perform all work in a well-ventilated area. Keep open flames (such as lit cigarettes) and unshielded lamp bulbs away from the work area. Immediately collect spilled fuel with rags and place them in a location where they cannot ignite spontaneously. If fuel gets on the skin, wash immediately with plenty of soap and water. When working on the fuel system, wear safety glasses and always keep a fire extinguisher within reach.

9. Fuel hoses are usually under pressure, so be prepared for fuel spray when disconnecting them and collect the fuel.

CAUTION

On vehicles equipped with fuel injection, the fuel system pressure must be relieved before servicing the fuel hoses.

10. Inspect all rubber fuel hoses for signs of wear and abrasion. Pay particular attention to

CAUTION

at bends and in front of fittings, for example where the hose connects to the fuel pump or filter, cracks may form.

11. Use only high-quality fuel hoses. Never, under any circumstances, use non-reinforced vacuum hoses, clear plastic tubing, or water hoses as fuel lines.

12. Band-type clamps are usually used to secure fuel hoses. Over time these clamps lose tension and may come loose during removal. When replacing hoses, replace such clamps with screw-type clamps.

13. Fuel leaks are difficult to pinpoint until the leak becomes significant and therefore easily visible. Fuel tends to evaporate quickly on contact with air, especially in a hot engine compartment. Small drops may disappear before you can locate the leak. If you suspect a fuel leak in the engine compartment, cool the engine, then start it while cold with the hood open. Metal parts contract when cooled, and rubber hoses tend to loosen, so any leaks will be more apparent while the engine warms up from a cold start. Metal Lines

14. Sections of metal tubing are often installed between the fuel pump and the fuel injection system. Carefully inspect these tubes for dents, kinks, or cracks.

15. If a section of metal line must be replaced, use only seamless steel tubing. Copper and aluminum tubing are not strong enough to withstand vibration caused by engine operation.

16. Inspect metal brake lines at their connections to the master cylinder and to the pressure regulator or ABS (if equipped) for cracks or loose fittings. Any sign of brake fluid leakage requires immediate thorough inspection of the entire brake system. Power Steering Hoses

17. Inspect power steering hoses for signs of fluid leakage, loose fittings, and worn clamps. Leaking hoses and worn clamps must be replaced. Cooling System Hoses

18. Coolant leaks are usually indicated by white or rust-colored deposits in the area adjacent to the leak.

19. Thoroughly inspect the radiator and coolant hoses along their entire length. Replace hoses that show cracks, splits, or signs of aging. Cracks are easier to detect when the hose is squeezed. Pay particular attention to

CAUTION

Do not overtighten the hose clamps that attach hoses to cooling system components. Overtightened hose clamps can cause a hose to split or puncture, resulting in coolant leaks. Inspect all hoses and hose connection surfaces for leaks. If any leak-related problems are found, replace the component or gasket.