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.
Thermostatic Air Cleaners -- All Models: Operation: Notes
When temperature of air entering air cleaner is less than the setting of temperature sensor, sensor closes to allow engine vacuum to operate vacuum motor which closes damper assembly to outside air. Air is then drawn from around exhaust manifold, through heat shroud and into air cleaner as heated air. As air inside air cleaner warms, sensor valve begins to open. This bleeds off vacuum to vacuum motor. As vacuum to vacuum motor drops, air control door begins to open, allowing outside air to enter air cleaner. When air entering air cleaner reaches a specified temperature, air control door opens completely, closing off heated air coming in from around exhaust manifold.
On American Motors 4.2L (258") 6-Cylinder engines, a vacuum motor controlled trap door is also used to close off the air cleaner when engine is not operating. This prevents fuel vapor from escaping into the atmosphere when engine is not operating.
Use the Manual With the Right Hardware
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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.