1981 Chevrolet Step Van P30, 5.7L Eng VIN M, Standard TransFACTORY OEM SERVICE PROCEDURE

Evaporative Emissions System: Testing

  1. With engine cold, position transmission in "NEUTRAL" or "PARK" and apply parking brake. Start engine and observe movement of actuator rod and exhaust heat valve. Valve should move to its closed position.
  2. If valve does not close, disconnect hose at actuator and check for vacuum. If there is vacuum, replace actuator. If no vacuum is found, disconnect hose at TVS-to-vacuum source. If there is vacuum at hose, replace TVS. If no vacuum, check hose for leaks.
  3. When coolant temperature reaches 180°F (V8) or oil temperature reaches 150°F (6 cylinder), exhaust heat valve should move to the open position.
  4. If valve does not open, disconnect hose at actuator and check for vacuum. If there is vacuum, replace TVS. If no vacuum is present, replace actuator.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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