What Causes Engine Noise After the Vehicle Is Turned Off?
2 Answers
Car engine noise after turning off the ignition can be caused by: 1. Cooling sounds from the three-way catalytic converter; 2. Cooling sounds from the exhaust pipe; 3. Cooling sounds from the turbocharger; 4. Abnormal noises due to uneven engine cooling. The function of the engine is to convert the thermal energy of gasoline into mechanical energy by expanding the gas after combustion in a sealed cylinder, thereby driving the piston to perform work. The components of the engine include: 1. Valve train; 2. Crankshaft and connecting rod mechanism; 3. Ignition system; 4. Cooling system; 5. Lubrication system; 6. Starting system; 7. Fuel supply system. Engine maintenance methods include: 1. Using qualified engine oil; 2. Using qualified coolant and antifreeze; 3. Regularly cleaning the radiator scale; 4. Regularly removing engine carbon deposits; 5. Regularly replacing the car's three filters; 6. Maintaining a reasonable engine speed.
I've been driving for over a decade, and this ticking sound after turning off the engine is very common. It's mainly due to the thermal expansion and contraction of the exhaust pipe, especially noticeable in winter. The exhaust pipe can reach several hundred degrees while operating, and the metal contracts when cooling down, causing the ticking sound—this is normal. However, if you hear particularly harsh metal scraping noises, it might be due to deformed or stuck cooling fins in the turbocharger. Last time, my neighbor's car made a rattling sound after shutdown, and the repair shop found that the ceramic core inside the catalytic converter had broken. If you hear a whistling-like squeak, it's likely due to insufficient lubrication in the pulley bearing. These unusual noises are particularly hard to pinpoint, so it's best to open the engine bay immediately after shutting off a warm engine to listen closely.
