Toyota RAV4 > Tune-up and routine maintenance > Underhood hose check and replacement

Underhood hose check and replacement

Caution: Never remove air conditioning components or hoses until the system has been depressurized.


1. High temperatures in the engine compartment can cause the deterioration of the rubber and plastic hoses used for engine, accessory and emission systems operation. Periodic inspection should be made for cracks, loose clamps, material hardening and leaks.

2. Information specific to the cooling system hoses can be found in Cooling system check.

3. Some, but not all, hoses are secured to the fittings with clamps. Where clamps are used, check to be sure they haven’t lost their tension, allowing the hose to leak. If clamps aren’t used, make sure the hose has not expanded and/or hardened where it slips over the fitting, allowing it to leak.

Vacuum hoses

4. It’s quite common for vacuum hoses, especially those in the emissions system, to be color coded or identified by colored stripes molded into them. Various systems require hoses with different wall thickness, collapse resistance and temperature resistance. When replacing hoses, be sure the new ones are made of the same material.

5. Often the only effective way to check a hose is to remove it completely from the vehicle. If more than one hose is removed, be sure to label the hoses and fittings to ensure correct installation.

6. When checking vacuum hoses, be sure to include any plastic T-fittings in the check. Inspect the fittings for cracks and the hose where it fits over the fitting for distortion, which could cause leakage.

7. A small piece of vacuum hose (1/4-inch inside diameter) can be used as a stethoscope to detect vacuum leaks. Hold one end of the hose to your ear and probe around vacuum hoses and fittings, listening for the hissing sound characteristic of a vacuum leak.

Warning: When probing with the vacuum hose stethoscope, be very careful not to come into contact with moving engine components such as the drivebelts, cooling fan, etc.

Fuel hose

Warning: Gasoline is extremely flammable, so take extra precautions when you work on any part of the fuel system. Don’t smoke or allow open flames or bare light bulbs near the work area, and don’t work in a garage where a gas-type appliance (such as a water heater or a clothes dryer) is present. Since gasoline is carcinogenic, wear fuel-resistant gloves when

there’s a possibility of being exposed to fuel, and, if you spill any fuel on your skin, rinse it off immediately with soap and water. Mop up any spills immediately and do not store fuel-soaked rags where they could ignite. The fuel system is under constant pressure, so, if any fuel lines are to be disconnected, the fuel pressure in the system must be relieved first (see Fuel pressure relief procedure). When you perform any kind of work on the fuel system, wear safety glasses and have a Class B type fire extinguisher on hand.

8. Check all rubber fuel lines for deterioration and chafing. Check especially for cracks in areas where the hose bends and just before fittings, such as where a hose attaches to the fuel filter.

9. High quality fuel line, specifically designed for fuel injection systems, must be used for fuel line replacement.

Warning: Never use anything other than the proper fuel line for fuel line replacement.

10. Spring-type clamps are commonly used on fuel lines. These clamps often lose their tension over a period of time, and can be sprung during removal. Replace all spring-type clamps with screw clamps whenever a hose is replaced.

Metal lines

11. Sections of metal line are often used for fuel line between the fuel pump and fuel injection unit. Check carefully to be sure the line has not been bent or crimped and that cracks have not started in the line.

12. If a section of metal fuel line must be replaced, only seamless steel tubing should be used, since copper and aluminum tubing don’t have the strength necessary to withstand normal engine vibration.

13. Check the metal brake lines where they enter the master cylinder and brake proportioning unit (if used) for cracks in the lines or loose fittings. Any sign of brake fluid leakage calls for an immediate thorough inspection of the brake system.

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