Intake Air Bypass Control Thermal Valve Test
  1. Start the engine, then let it idle.
    NOTE: Engine coolant temperature must be below 65 °C (149 °F).
  1. Remove the intake manifold cover. Remove the vacuum hose (A) from the intake air duct, and connect a vacuum pump/gauge (B) to the hose.
  1. Raise and lower the engine speed, and make sure the vacuum gauge reading changes as the engine speed changes.
    If the vacuum reading does not change, check for these problems:
  1. Hold the engine speed at 3,000 rpm (min −1 ) without load (in neutral) until the radiator fan comes on, then let it idle.
  1. Raise and lower the engine speed, and make sure the vacuum gauge reading does not change as the rpm changes.
    If the vacuum reading changes, check for these problems: