Because of the high temperature level in the hood, rubber and plastic hoses that are utilized in engine, accessory, and emission systems wear out and crack, and should be checked frequently for cracks, loose clamps, material hardening, and leakage. Most hoses are held in place by clamps, and these should be checked for tightness to avoid leakage; where there are no clamps, check whether the hose has swelled or hardened at the fitting. The PCV system develops a path for crankcase blow-by gas by connecting a thin rubber hose from the crankcase to the intake manifold before the air-fuel mixture is actually ignited, so a PCV hose ought to be inspected for cracks or blockage. Vacuum hoses, if they are color-coded should be replaced with hoses of similar material and wall thickness and might as well remove and label the hoses for ease of reconnection. A partial list of what is visible through the inspection window on plastic T-fittings includes cracks and distortion of hoses associated with leakage, as well as vacuum hose tremors that cause vacuum leaks; to listen to the vacuum leak, insert a small piece of vacuum hose into the engine compartment and try not to move engine parts. Whereas working on the fuel system, one has to be very careful owing to the radioactivity of gasoline; should wear fuel-resistant gloves and safety glasses besides noting the availability of minimum Class B fire extinguisher. Looking for signs of wear especially at bends and fittings to flexible fuel lines and only use the fuel lines that is suitable for the fuel injection system when replacing them. Such connections as spring type clamps should be replaced with screw clamps and special tools may be required for couplings having spring lock type. Wireing should be checked for bends, crimps or cracks where it is used between the fuel pump and the fuel injection unit; seamless steel tubing for replacement as copper and aluminium are lack strength. Also, metal brake lines should be inspected for signs of cracks and looseness of the fittings though any sign of brake fluid leakage will call for further examination of the brake system.