What to Do When There's a Hissing Sound After Turning on the Car?

[DelMatteo]

Applying adhesive strips on doors and windows or placing rubber pads in friction-prone areas may help reduce or eliminate the abnormal noise. If the unusual noise originates from the engine, it usually indicates a major malfunction, and it's advisable to send the car for professional inspection and repair as soon as possible. If the tire noise is severe, accompanied by noticeable body shaking or even deviation in direction, it might indicate a tire blowout, and immediate tire replacement is recommended.

[DeDelaney]

I've also heard this hissing sound while driving, which often scares new car owners into thinking there's an air leak or a major issue. Most of the time, it's actually normal—like when the AC starts up and releases cold air or adjusts pressure, creating a "hissing" noise. My advice: don't panic and drive off immediately. First, find a safe spot to pull over and check: listen if the sound comes from near the AC vents (correct location means it’s likely fine); also watch for warning lights on the dashboard, like coolant or battery alerts. If the noise stops quickly, no worries. But if it persists with odd smells (e.g., burning rubber), head to a repair shop ASAP to inspect the air pump or seals—ignoring it could lead to costlier fixes. During routine maintenance, ask technicians to pay extra attention to the air pressure system. Building this habit helps avoid such scares.

[OCollin]

After driving for a long time, such a hissing sound after power-on becomes quite common. I guess the sound you described is similar to a tire valve leaking or the air conditioning compressor working. The former is mostly caused by unstable tire pressure or a loose valve, while the latter is part of the normal startup process. Here’s a simple self-check suggestion: First, turn off the air conditioning to see if the sound disappears; then, check the tire pressure to see if it’s balanced—if not, it indicates a leak. Listen carefully to locate the sound: if it’s near the engine, it might be a problem with the air pump; if it’s under the car, check the suspension airbags. If the sound is loud and persistent, don’t force yourself to drive. I once encountered a similar issue and fixed the air pump problem early, saving myself from major repairs later. Develop a habit of checking tire pressure monthly to prevent such issues—a simple tire pressure gauge will do the job in seconds.

[Emerson]

From a maintenance perspective, this venting sound is often associated with the pneumatic control system. I speculate it could be either normal exhaust from the air conditioning evaporator, or air leakage during the self-test of the air suspension system when powered on. Step-by-step troubleshooting is recommended: First, use your ears to locate the sound - short compressor or air pump noises near the engine compartment are normal; sounds from under the vehicle may indicate poor sealing of suspension air tanks. Record the sound with your phone and compare changes when parked. Abnormal signs like rapid hissing accompanied by pressure gauge drops require professional inspection. Regularly check pressure stability with a personal tire gauge to prevent minor issues like seal aging causing leaks. Addressing these details early can save significant repair costs.