What Causes the Continuous Abnormal Noise After the Magotan Shuts Down?

[McEmerson]

The main reasons for abnormal noise after the vehicle shuts down are as follows: 1. Abnormal noise caused by excessively high tire pressure. 2. Abnormal noise caused by uneven tire wear. The tread area of the tire contacts and rubs against the ground. If the tread area wears unevenly and has bumps, it will produce a buzzing sound. 3. Abnormal noise due to damaged wheel hub bearings. Worn wheel hub bearings will generate a buzzing sound, mainly caused by long-term use leading to wear and looseness of the wheel hub bearings. The reasons for abnormal brake noise without pressing the brake pedal are as follows: 1. Use of low-quality or overly hard brake pads: If low-quality or overly hard brake pads are used, they will produce a squeaking sound when rubbing against the brake disc during braking. Therefore, it is essential to use high-quality brake pads when replacing them. 2. Presence of sand or foreign objects between the brake pad and brake disc: During normal driving, it is inevitable to pass through some complex road conditions. Due to the unique design of disc brakes, some sand and foreign objects may get between the brake pad and brake disc, causing abnormal noise during braking.

[StMatthew]

I've been driving Volkswagen cars for over a decade, and it's quite common to hear sounds after shutting off the Passat. The most frequent is the 'crackling' noise from the exhaust pipe due to thermal expansion and contraction. Sometimes the turbo cooling fan may keep running for a few minutes. If you hear metallic knocking sounds from the undercarriage, it might be due to aged or loose exhaust pipe hangers. Once I encountered a 'ticking' sound near the fuel tank, which turned out to be the carbon canister purge valve working to extract gasoline vapors. These sounds are more noticeable during the break-in period of new cars. If you've just driven at high speeds and shut off the engine, the cooling and contraction of metal components in the engine bay can also produce clinking sounds. However, if you hear any harsh scraping noises, immediately check if the undercarriage brackets are cracked.

[VonElisa]

When repairing cars, this situation is often encountered. Focus on checking three areas: The thermal expansion and contraction sound of the exhaust pipe when cooling is the most typical, especially more noticeable in summer when temperatures are high; the turbo cooling system continues to operate, and the fan may run for 3-5 minutes; the carbon canister purge valve still cycles fuel vapor after the engine is turned off, producing a rhythmic ticking sound. For metallic knocking sounds, pay attention to the exhaust pipe hangers and chassis rubber bushings. Volkswagen cars, after five or six years, are prone to aging of these rubber components. If you hear continuous abnormal noises in a quiet garage, it is recommended to lift the chassis and check if the exhaust gasket is leaking.

[VonJourney]

Last month, my Magotan had the same issue—there was always a 'ticking' sound under the car after turning off the engine. The 4S dealership said it was normal, caused by the cooling of high-temperature exhaust components. However, I later noticed the sound persisted for half an hour, and upon inspection, it turned out the rubber hanger connecting the exhaust pipe to the chassis had cracked. The mechanic explained that German cars have longer exhaust systems, which undergo significant contraction during cooling, causing aged hangers to make unusual noises. Now, during every maintenance session, I have them inspect the chassis rubber components and clear any accumulated water in the exhaust pipe to minimize such sounds.

[Lisa]

In principle, the abnormal noise after engine shutdown is primarily a thermodynamic phenomenon. When the temperature in the engine compartment drops rapidly, the aluminum alloy exhaust pipe contracts faster than the cast iron, causing noise due to the differential contraction of different materials. The cooling process of the turbocharger bearings also produces high-frequency noise. Volkswagen's EA888 engine is additionally designed with a delayed cooling cycle, where the water pump continues to operate for a few minutes. If you hear a whistling-like sound, it might be the turbo wastegate valve resetting. It is recommended not to walk away immediately after parking; observing the source of the sound can make it easier to diagnose.