How to Solve the Abnormal Noise When the Car Stalls?

[DiEliza]

When the three-way catalytic converter stops working, the temperature will drop, causing thermal expansion and contraction of its internal metal components, which then produces abnormal noise. This noise cannot be eliminated. If the screws at the interface of the three-way catalytic converter are loose, simply tighten them. If the carbon canister solenoid valve is damaged, replace it with a new one.

[DeAbigail]

I've noticed that many car owners encounter strange noises when the engine is turned off. Based on experience, the most common sound is the cracking noise from the catalytic converter cooling down due to thermal expansion and contraction, which is usually a normal physical reaction and nothing to worry about. However, if it's a sharp squeaking or clanging sound, you should be alert. For example, a loose or aged alternator belt can cause friction noises, or the air conditioning compressor belt may be worn out. Even a loose exhaust pipe bracket can produce metallic rattling sounds after the engine is turned off. I usually start by identifying the location of the sound to pinpoint the issue. For engine-related noises, I check the belt tension and make slight adjustments with a wrench, while for sounds underneath, I inspect the exhaust pipe for stability. To ensure safety, it's best not to ignore these small signals. Regular full inspections at a repair shop can prevent bigger problems, especially for older vehicles that require more frequent maintenance.

[OAriana]

As an average driver, I find this quite common. There are usually minor sounds after turning off the engine, like the turbo cooling down or the catalytic converter contracting, which are mostly harmless. However, unusual noises like the fan still running or the belt squeaking deserve attention. A friend's car once had abnormal sounds due to belt issues and eventually needed a replacement part to fix it. My suggestion is to first identify the type of sound. If it sounds like mechanical friction, it's best not to delay and get it diagnosed at a repair shop immediately. Also, during routine maintenance like oil changes, have the belt condition checked to prevent small issues from escalating into major problems affecting driving safety.

[LucilleLynn]

I personally believe that abnormal noises after engine shutdown should not be taken lightly, as they could be precursors to serious malfunctions. For instance, bearing wear might produce a rattling sound, or a risk of belt breakage could lead to engine issues or even fire hazards. I would immediately pull over and have a professional technician conduct a comprehensive inspection with proper equipment. Meanwhile, I'd pay attention to the source of the noise: if it's from the chassis area, check the exhaust pipe bracket; if it's from the engine compartment, inspect the belt system. For prevention, regular vehicle maintenance such as a full inspection every six months can effectively reduce the occurrence of such abnormal noises.