Why Do I Hear Hissing Sound When Pressing Brakes?

If you notice a hissing sound when pressing brakes while inside the passenger cabin, that’s the sign of a faulty braking system. There are many reasons behind every sound reacted by the car. They should be diagnosed and fixed then and there. Missing your service will develop new varieties of problem, in the car.

Do You Hear A Hissing Sound When Pressing Brakes?

When the engine is working, and you’re not applying the brakes, the engine vacuum is applied equally to both sides of the diaphragm, so you get no braking assist. As you use the brakes, a valve opens, allowing atmospheric pressure to flow into one side of the diaphragm. Engine vacuum then pulls the diaphragm into the hydraulic brake cylinder, forcing the pushrod into the hydraulic brake cylinder.

If the atmospheric valve leaks air, and you’ll notice hissing sounds from brakes while you’re inside the cabin. This is often a relatively easy fix. Remove the two bolts holding the hydraulic brake cylinder in place and pull it away from the vacuum booster. Then disconnect the pushrod from the pedal. Next, remove the four bolts or nuts holding the vacuum booster onto the firewall.

What Causes Hissing Sound?

Let’s look at hissing and other noise created by an inadequate braking system.

1. Brake Hissing:

A hissing sound when pressing brakes is usually the brake booster leaking air. There could be a leak within the vacuum line, the booster diaphragm, or the hydraulic brake cylinder. A tiny leak could cause a hissing sound once you continue the pedal or excuse. The brake booster features a foam silencer that’s imagined to mask the noise of normal operations. When the froth silencer goes missing or is broken, you hear things that have always been there but were silenced before.

2. Rotor Grinding:

A grinding sound generally comes on suddenly until it’s so loud you can’t ignore it anymore. It’s caused by exhausted restraint rubbing on the brake rotor. If you let it go too long, the worn pads can damage the rotor, so they’ll get to get replaced also. If you’re lucky, it’d be just a pebble stuck within the calipers that might fall out on its own. Either way, it’s best to urge this checked as soon as possible.

3. Pad Squeaking:

Blame your brake pad material for that squeaking noise once you stop. Low-quality restraints tend to make more noise than higher-quality options. If the brakes squeak while you’re driving, the brake wear indicator on the pad is hitting the rotor. This is often a simple thing: the brake pads tell you it’s time to vary them.

4. Caliper Clicking:

This noise comes from brake components contacting another piece of metal. The brake pad could even be loose within the caliper seat, or the caliper itself could even be loose. A bent backing plate on the brake pad could be rubbing against the rotor or caliper. Clicking sounds also can come from other components, just like the CV joint.

5. Brake Rubbing:

A rubbing sound could be an early symptom of a worn brake pad rubbing against the rotor. The pad could be in the beginning stage of wear and tear and tear before moving on to a crucial grinding noise. Another possibility could also be a braking pad that hasn’t been fully released.

If you haven’t driven your car for a short time, there could even be rust on the rotors. Driving a few miles in stop-and-go traffic should look out of it. Another cause could also be a bent wheel rim caused by hitting a pothole or curb. The bent rim can rub against the caliper.

6. Creaking:

This is commonest at slow speed braking, caused by a caliper piston-to-seal interface. It’s usually solved by applying lubricant to a sticking caliper piston.

How To Take Care Of Your Brakes?

Follow the steps to get rid of a hissing sound when pressing brakes.

  1. Have your brake and restraint checked once a year. If they’re too worn to work properly, have them replaced. The booster uses a rubber diaphragm and a pushrod. The rod is connected to one side of your pedal, and thus the opposite side pushes the hydraulic brake cylinder piston.
  2. Check your brake fluid regularly. Your vehicle’s brake fluid is vital to transfer heat to all or any parts of the brakes and absorb water. If the fluid could also be a dark color, it’s getting to be time to possess it flushed.
  3. Listen and wait for the warning signs. These may include unusual noises, strange brake response, and abnormal feeling once you continue the brakes, which they’ll indicate a dangerous problem that you should have verified directly.
  4. The vacuum boosters use engine vacuum to increase braking power. So major fault in it will cause hissing noise when pressing brakes. Please consult with a professional to fix it.
  5. While driving, try coasting to the hamper before applying brakes. This helps your car’s brakes by putting less pressure on them.
  6. Avoid braking when cars before you put brake unnecessarily. As an example, they’ll be following too closely to the vehicle before them once you’ve got many distances to the coast. Hamper and keep a significant distance behind them, not only to preserve your brakes but also for safety purposes.
  7. Invest in good, reliable brakes. They’ll cost a slight bit extra, but they go to form a difference at the top of the day in terms of efficiency, safety, and sturdiness.


Safety is very crucial in our living status and technology. Do every possible method to maintain your car in perfect condition. Brakes are an essential component in the car, and you can avoid the hissing sound when pressing brakes by holding well with smooth usage.

I hope you made use of this article and share your thoughts. Have a fabulous day!

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