Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1973CHEVELLE 2D COUPE, 5.7L ENG VIN JREPAIR AND DIAGNOSISENGINE MECHANICALAUXILIARY EMISSION CONTROL SYSTEMSGENERAL MOTORS THERMAC AIR CLEANERTESTING
1973 Chevrolet Chevelle 2D Coupe, 5.7L Eng VIN J
General Motors THERMAC Air Cleaner: Testing
1973 Chevrolet Chevelle 2D Coupe, 5.7L Eng VIN JSECTION Testing
- Tape a thermometer in air cleaner next to temperature sensor. If temperature in engine compartment is more than closing temperature of sensor, let air cleaner cool to at least 7° below closing temperature of sensor. Install a tee in vacuum line at vacuum motor and connect a vacuum gauge in line.
- With engine off, control damper will be open (check visually). Install cover on air cleaner (without wing nut) and start engine. With engine at idle and ambient temperature below closing temperature of sensor, damper should close.
- When damper in snorkel begins to move toward open position, quickly remove cover on air cleaner and check thermometer and vacuum gauge. Vacuum should be 5-9 in. Hg when damper is closed to outside air.
- Replace cover and wait until damper is fully open, again note vacuum and temperature reading. Vacuum should be 3 in. Hg or less and temperature should be at opening temperature of sensor. If temperature is not within specifications, but vacuum is correct, replace sensor. If both temperature and vacuum are not within specifications, replace vacuum motor.NOTE: Temperature sensor is preset at factory. Do not adjust.
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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.