Why is there a hissing sound from the rear wheels after the Bora stalls?

[McCarter]

It may be the sound of coolant being pushed into the overflow tank by water vapor inside the cooling passages as the water temperature rises. After prolonged driving, it is recommended to let the engine idle for a while until the electric fan stops working and the water temperature returns to normal before turning off the engine. It could also be the sound of the turbocharger releasing pressure and cooling down. If the car is left running without stalling: The engine will remain in an idle state, continuously injecting fuel. Under idle conditions, fuel consumption is obviously higher than at economical speeds. Prolonged idling increases engine wear: If the car idles for too long, the oil pump speed decreases, resulting in lower oil pressure. This makes it difficult to effectively lubricate components such as bearing shells, thereby increasing wear on the pistons, connecting rods, and the engine itself.

[StCameron]

I've been driving a Bora for several years, and sometimes after turning off the engine, there's a slight hissing sound near the rear wheels, which feels like air leakage. Actually, this is mostly normal because the vacuum booster in the braking system releases its vacuum reserve after the engine is turned off, producing this sound. The vacuum booster operates using engine vacuum, and it automatically vents to protect the system once the engine is off. The sound usually lasts from a few seconds to half a minute before stopping. However, if the sound is particularly loud or the car body shakes, you should be alert to whether a tire has been punctured by a nail or if the brake pads are severely worn, causing abnormal venting. You can perform a simple check yourself: spray soapy water on the tire sidewalls and rims to see if bubbles emerge, or pay attention to whether the brake pedal becomes harder or if there are any abnormalities while driving. Regular maintenance, such as checking tire pressure and the braking system, can reduce unexpected risks. Don't panic—most of the time, it's nothing serious, but it's good to do a routine check for safety's sake.

[LeAiden]

The hissing sound from the rear wheels after turning off the Volkswagen Bora is usually a normal phenomenon caused by the brake vacuum booster releasing vacuum. The booster accumulates vacuum internally to assist with easier braking, and the hissing sound occurs as the vacuum slowly dissipates after engine shutdown. This is by design to prevent system overpressure damage. If the sound is sharp or prolonged, it might indicate a punctured tire or a damaged seal in the suspension system's shock absorber causing pressure leakage. Listen to the sound source: if it's near the brake pedal, it's fine; if it's close to the wheel hub, the issue could be more serious. Check if the tire valve core is loose and use a tire pressure gauge to ensure stable pressure. It's advisable to clean debris under the wheels during car washes and regularly replace tires or perform wheel alignment maintenance to prevent potential hazards. These are small details for safe driving—if the sound is loud, visit a professional shop for diagnosis without delay.

[VonBrielle]

Back when I drove my Bora, I often heard a hissing sound from the rear wheels after turning off the engine, like air leaking. At first, I panicked, thinking I might have run over something. After consulting my mechanic friend, I learned it was actually the vacuum pressure release sound from the brake booster—a common design in modern cars. If the sound is brief, it's normal. But if it's accompanied by soft tires or unstable driving, there might be a real air leak issue. Checking it yourself is simple: look for obvious dents on the tires and lightly kick the wheels to listen for airtightness. Don’t overlook routine maintenance, like checking tire pressure during seasonal changes to avoid potential issues from road bumps. Safety first—developing a habit of regular checks always brings peace of mind.