Mercedes-Benz SL400 Hissing noise when brake pedal is depressed Inspection at your home or office.

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Hissing noise when brake pedal is depressed Inspection Service

How much does a Hissing noise when brake pedal is depressed Inspection cost?

On average, the cost for a Mercedes-Benz SL400 Hissing noise when brake pedal is depressed Inspection is $95 with $0 for parts and $95 for labor. Prices may vary depending on your location.

CarServiceEstimateShop/Dealer Price
2015 Mercedes-Benz SL400V6-3.0L TurboService typeHissing noise when brake pedal is depressed InspectionEstimate$114.99Shop/Dealer Price$132.49 - $145.62
2016 Mercedes-Benz SL400V6-3.0L TurboService typeHissing noise when brake pedal is depressed InspectionEstimate$94.99Shop/Dealer Price$112.52 - $125.67
Show example Mercedes-Benz SL400 Hissing noise when brake pedal is depressed Inspection prices

Brakes are the most important safety components on your vehicle. Despite that importance, it’s easy to take them for granted, at least until your car begins to do strange things. Ordinarily, pressing your brake pedal should result in only the car slowing down or stopping. If you hear a hissing noise when the brake pedal is depressed, it may mean there’s something that needs to be repaired in the system.

How this system works:

On many cars, the master cylinder works in tandem with a brake booster. The brake booster is mounted to the firewall, generally in front of the steering wheel position, and the master cylinder attaches to it. The entire point of the brake booster is to make it easier to press the brake pedal and slow or stop the car.

Your brake booster works on vacuum pressure. There’s a diaphragm inside that is responsible for maintaining pressure when you’re not pressing the pedal. However, when you do press the pedal, a push rod moves forward within the booster and into the master cylinder. The side of the diaphragm facing the cabin vents to atmospheric pressure, while vacuum is maintained on the other side.

This then equalizes with pressure on the other side of the diaphragm, providing the boost needed to make pressing your brake pedal easier. The hissing noise you hear when the brake pedal is depressed could be nothing more than ordinary operation, or it could be a sign of a deeper problem. There are a couple of different potential issues here, some more severe than others.

Common reasons for this to happen:

  • Leaking Vacuum Line: Your brake booster is supplied with vacuum from the engine via a vacuum hose. It’s usually located near the firewall. If this hose has a leak, it can be heard within the cabin.

  • Leaking Brake Booster Diaphragm: The diaphragm that’s responsible for maintaining pressure within the brake booster can fail, particularly if the master cylinder is leaking fluid into the booster. When this happens, you’ll hear a hissing sound when depressing the brake pedal, but the pedal itself will be much, much harder.

  • Damaged or Missing Foam Silence: Most cars equipped with brake boosters also have a foam silencer that’s designed to help prevent you from hearing that hissing sound. If the silencer has degraded or been damaged, you’ll hear the hissing sound.

  • Failing Master Cylinder: If you hear a hissing sound and suspect that the problem is the diaphragm in the booster, the actual cause is likely the master cylinder beginning to fail. Signs that the master cylinder is leaking into the brake booster include low fluid in the reservoir with no visible leaks.

What to expect:

A top-rated mobile mechanic will come to your home or office to inspect your brake system, including the brake pedal operation, the brake booster and listen to the hissing sound. The mechanic will then provide a detailed inspection report that includes the scope and cost of the necessary repairs.

How it's done:

The mechanic will need to crank the car in order to verify the hissing sound, and a test drive may be necessary to duplicate the complaint. Additionally, the mechanic will inspect the brake pedal operation, the condition of the brake booster, the master cylinder, the level of fluid in your system and more.

How important is this service?

Power brakes are wonderful things, making it far easier to work a brake pedal that would otherwise require significant force to activate. While the hissing sound may be a sign of nothing more dangerous than a failed piece of foam, it could be a symptom of something much more worrisome – a damaged brake booster and a failing master cylinder. You cannot afford to take chances with your brake system. One of our professional mechanics can inspect the entire system and determine if there’s cause for concern, and what needs to be done if there is a problem.

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5,332
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David

10 years of experience
172 reviews
David
10 years of experience
Mercedes-Benz SL400 V6-3.0L Turbo - Pre-purchase Car Inspection - Orlando, Florida
Pre-Purchase service - On time with appointment. Follow up call and report was generated immediately which is greatly appreciate. Many thanks!!

Lee

38 years of experience
228 reviews
Lee
38 years of experience
Mercedes-Benz SL550 V8-5.5L - Headlight Bulb Replacement (Driver Side Low Beam, Passenger Side Low Beam) - Oklahoma City, Oklahoma
Was my first time to use YourMechanic. I appreciate the experience and knowledge of Lee, the mechanic. The online automatic system could be greatly improved due to wait time and trouble authorizing credit card, etc.

James

41 years of experience
112 reviews
James
41 years of experience
Mercedes-Benz S550 V8-4.6L Turbo - Check Engine Light is on - Bedford, Ohio
He was professional. He took time to explain each issue in terms that were understandable.

Sean

17 years of experience
111 reviews
Sean
17 years of experience
Mercedes-Benz 190E L4-2.3L - Electric Problems - Washington, District of Columbia
First, Sean arrived on time. He asked pertinent questions about my most recent car service, after which, he immediately diagnosed, determined, and solved the frequent draining of my car battery by removing the radio, unplugging radio cables, and neatly reinserting the radio, which is all of what I requested and wanted to happen.. Sean Brown appeared to have a high automobile IQ combined with valuable learned experience, and he was courteous, polite, friendly, and very professional in completing his tasks and requirements. Anyone who gets him for their job will probably be very, very satisfied and happy that he was the one who came.

Excellent Rating

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Rating Summary
5,332
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5,332
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123
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