···
Log in / Register

What Causes the Hissing Sound When Braking?

4 Answers
LaEvangeline
07/30/25 12:06am
The reasons for hearing a hissing sound when braking are as follows: 1. When you press the brake pedal, you can clearly hear a leaking sound, and sometimes a hissing sound after pressing the pedal. In this case, the initial judgment is that there might be an issue with the brake booster. 2. The leaking sound generally falls into two scenarios: one occurs during the normal operation of the brake booster but is only brief; the other happens after pressing the pedal, with a more noticeable or continuous sound. Additional Information: 1. To check if the sound is caused by a leaking brake booster: Start the engine, let it run for 1~2 minutes, then turn it off, and press the pedal three times. For a normally functioning vacuum booster, the first press will have a normal pedal travel due to sufficient vacuum in the booster; the second press will show significantly reduced travel as some vacuum has been lost; by the third press, with very little vacuum left in the booster, the pedal travel will be minimal, and further pressing will be difficult. 2. This is the so-called "each press higher than the last." It proves the booster is not leaking and is functioning properly. If each pedal press has minimal and unchanged travel, known as "extremely hard pedal," it indicates the booster is leaking and failing. Severe leaks can produce audible sounds, and a leaking booster should be replaced.
Was this review help?
20
5
Share
Carlos
08/16/25 4:00am
I have the same issue when driving - hearing a hissing sound like the car is sighing whenever I brake. This usually indicates a problem with the brake booster system, specifically air leakage from the vacuum hose or booster, causing air to escape during normal operation. The vacuum system relies on engine assistance to make braking easier, and when it leaks, not only does the sound occur, but in severe cases, the brake pedal becomes stiff and hard to press, which is extremely dangerous, especially in rainy conditions or at high speeds. Last time my car had this issue, I thought it was minor and delayed fixing it, but during an emergency brake, I almost rear-ended another car - luckily nothing serious happened. I immediately took it to the repair shop, and they found the booster connection was loose - just needed a small part replacement. Now I pay attention to any unusual brake noises and make sure to check these areas during regular maintenance. Safety first - don't try to save money or cut corners.
Was this review help?
6
1
Share
Expand All
DeWalker
10/19/25 5:56am
A hissing sound when braking is mostly caused by issues with the vacuum booster or related pipelines. The vacuum booster uses engine vacuum to assist braking. If there's a leak—such as aging pipes or cracked joints—air passing through can create that hissing noise. A significant leak weakens brake assistance, making the pedal hard to press and reducing braking effectiveness, especially when carrying loads or going uphill, which poses high risks. I recommend not delaying—stop immediately to check simple areas, like opening the hood to inspect pipelines for obvious cracks or looseness. If you're unsure, don’t tamper with it; get it repaired right away. From my experience, fixing this isn’t expensive, but ignoring it can lead to major trouble. Once repaired, driving becomes worry-free. Regularly inspect vacuum system connections during maintenance to prevent issues proactively.
Was this review help?
9
4
Share
Expand All
MacAlivia
12/02/25 6:32am
A hissing sound when braking is usually caused by a leak in the vacuum booster system, such as a damaged vacuum hose or failed booster seal, allowing air to enter the booster chamber and create noise. This prevents the system from functioning properly, increases brake pedal resistance, and worsens braking performance, which can be particularly dangerous during long drives or on slippery roads. It is recommended that owners stop driving immediately upon noticing this issue and have a professional technician use diagnostic tools to locate the leak. Replacing or repairing vacuum system components is straightforward, so avoid attempting DIY fixes. Regularly monitor brake sounds to prevent minor issues from escalating.
Was this review help?
11
1
Share
Expand All
More Forum Discussions

Will I Be Fined for Driving with the Trunk Open?

Driving with the trunk open is considered a traffic violation, and the vehicle may be stopped by traffic police and penalized. Generally, this results in a fine, but the driver may only receive a warning without any points deducted. Upon being reminded by the traffic police, the driver must promptly close the trunk securely. According to Article 9 of the 'Measures for the Scoring Management of Road Traffic Safety Violations,' if the trunk being open blocks the license plate, it constitutes the violation of 'intentionally obscuring the license plate.' In such cases, the traffic management authorities will impose a fine and deduct 12 points. Additionally, an improperly closed trunk can obstruct the driver's visibility and affect safe driving, potentially interfering with other vehicles and pedestrians on the road. The traffic police may impose a fine and deduct three points, as this situation can easily lead to traffic accidents and poses significant safety hazards. Therefore, the traffic police may impose stricter penalties on the driver to prevent such behavior from recurring. According to Article 62 of the 'Regulations for the Implementation of the Road Traffic Safety Law of the People's Republic of China,' the following acts are prohibited while driving a motor vehicle: driving with the doors or trunk not properly closed; hanging or placing items within the front or rear windows that obstruct the driver's view; making or receiving handheld phone calls, watching TV, or engaging in other activities that hinder safe driving; stalling or coasting in neutral on steep slopes; or throwing items onto the road. If there are items in the trunk, they may be lost when driving on bumpy roads, leading to financial losses. If these items cause damage to vehicles behind, the driver may also be liable for repair costs.
9
0
Share

Differences Between Honda XR-V and CR-V

Differences between Honda XR-V and CR-V are as follows: 1. Models: The latest top-end model of Honda XR-V is the 2021 220TURBO CVT Flagship Edition, while the latest top-end model of Honda CR-V is the 2021 Sharp Hybrid 2.0L 4WD Pure Enjoy Edition. 2. Price: The official price of the top-end Honda XR-V is lower than that of the top-end Honda CR-V. 3. Overall Body: The body of the top-end Honda XR-V is shorter than that of the top-end Honda CR-V, and the wheelbase of the top-end Honda XR-V is also shorter than that of the top-end Honda CR-V. 4. Overall Configuration: The top-end Honda CR-V is more richly equipped than the top-end Honda XR-V.
11
0
Share

What is the 0-100 km/h acceleration time for the Sylphy?

According to official data, the 1.6L Sylphy model has a 0-100 km/h acceleration time of 12.1-12.2 seconds. Factors affecting a vehicle's 0-100 km/h acceleration time are as follows: Torque: Torque, in layman's terms, represents how much force is available. The greater the torque, the more force is available to propel the vehicle, resulting naturally in faster acceleration. The Audi R8 has a maximum torque of 570 Nm and a 0-100 km/h acceleration time of 3.1 seconds. The Sylphy has a torque of 155 Nm and a 0-100 km/h acceleration time of 12.1 seconds. Transmission efficiency: The transmission is the medium for transferring power and inevitably involves power loss. The higher the transmission efficiency, the better the acceleration performance. Generally, transmission efficiency ranks as follows: manual transmission > dry dual-clutch transmission > wet dual-clutch transmission > AT transmission > CVT transmission. The Sylphy is equipped with a CVT continuously variable transmission. Power-to-weight ratio: The relationship between horsepower and vehicle weight is called the power-to-weight ratio (unit is Hp/T). The higher the power-to-weight ratio, the faster the acceleration. The Audi R8 has a power-to-weight ratio of 373 Hp/T and a 0-100 km/h acceleration time of 3.1 seconds. The Sylphy has a power-to-weight ratio of 103 Hp/T and a 0-100 km/h acceleration time of 12.1 seconds.
3
3
Share

What is the Seizure Status of a Motor Vehicle?

Vehicle seizure status refers to a vehicle that is prohibited by the court from undergoing registration, modification, transfer, mortgage release, deregistration, or pledge release due to reasons such as economic debt disputes. Below is a detailed introduction to seized vehicles: 1. Overview: A seized vehicle is one that is prohibited by the court from undergoing registration, modification, transfer, mortgage release, deregistration, or pledge release due to reasons such as economic debt disputes. 2. Other Information: According to Order No. 124 of the Ministry of Public Security, it clearly stipulates the operations prohibited during the seizure period, namely registration, modification, transfer, mortgage release, deregistration, and pledge release; however, operations such as annual inspections, temporary license plates, and replacement of license plates are not prohibited.
16
3
Share

Why Are There So Many Used Volkswagen Tayron SUVs?

The reasons for the abundance of used Volkswagen Tayron SUVs are as follows: It may be due to the low resale value or satisfaction ratings of Volkswagen SUVs. Specific explanations are provided below: The Volkswagen Tayron is positioned as a midsize SUV. In the hot comparison model reputation ranking, it ranks second with a score of 4.44, with its power and comfortability both ranking first. Relevant information about the Tayron is introduced below: 1. New vehicle dimensions: The vehicle length is 4590mm, the wheelbase is 2731mm, the fuel tank capacity is 63 liters, the luggage compartment capacity is 506-1590 liters, it uses 95-octane gasoline, and features front MacPherson + rear multi-link independent suspension. 2. Configuration: The new vehicle is equipped with tire pressure warning, active braking, front and rear parking radar, cruise control, panoramic sunroof, 8-inch LCD instrument panel, supports CarPlay+CarLife+original factory mapping/screen mirroring, LED automatic combination headlights, electric exterior rearview mirrors + heating, one-touch up/down for all windows + anti-pinch, automatic anti-glare rearview mirror, automatic climate control with PM2.5 filter, and other features.
6
4
Share

What are the differences in annual inspections between seven-seater and five-seater vehicles?

Five-seater vehicles enjoy a six-year exemption from inspection policy. For new vehicles within six years, owners only need to go to the vehicle management office to obtain the annual inspection sticker. Below is relevant information about vehicle annual inspections: 1. Time: For passenger cars and blue-plate minivans, within the first six years after new vehicle registration, inspections are required every two years; after six years, inspections are annual; after ten years, inspections are annual, and after fifteen years, inspections are required twice a year. For trucks, inspections are annual after registration, and after ten years, inspections are required twice a year. 2. Regulations: If a vehicle is found by traffic police on the road without an annual inspection, the owner may be fined or the vehicle may be impounded. Additionally, in insurance contracts, vehicles that have not undergone timely annual inspections are considered unqualified, and no claims will be paid in the event of a vehicle insurance accident.
20
0
Share
Cookie
Cookie Settings
© 2025 Servanan International Pte. Ltd.