brake hissing sound - Honda-Tech - Honda Forum Discussion

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brake hissing sound

Old 06-11-2018, 10:33 PM
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Icon4 brake hissing sound

I have recently changed my rear brake pads on my 08 accord, after changing the pads i go to test the car and i find that i have a spongy pedal. So i bleed the brakes using the 2 person method but i still have a spongy pedal, however the brake pedal is soft all the way until it comes close to the floor then it gets hard. when i tried to brake the brakes where hardly grabbing until pressing the pedal almost all the way. I also started to hear a new hissing sound coming from the brake pedal and near the brake master cylinder and brake booster. this makes me having to press the brakes way before i intend to stop.
I'm thinking about changing both my master cylinder and brake booster but i want to know if there could be another problem, because the master cylinder and brake booster are not cheap.
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Old 06-12-2018, 09:58 AM
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Default Re: brake hissing sound

The hissing when depressing the brakes is probably normal vacuum assist.

You likely have air in your lines. The 2 person method is useless. Ditch the 2nd person. Embrace loneliness and efficiency. All you need is a bottle, some brake fluid, and a vacuum line to make a 1 person bleeder.

Did your master cylinder succ in air because the 2nd person allowed the fluid level to drop too low whilst bleeding the brakes? If so...probably you'll need a dealer to do an ABS unit bleed.

Also...was the engine running while yall were bleeding brakes? It sure should be.

Pro tip: Don't push the brake pedal to the floor when bleeding the brakes. You run the risk of damaging the master cylinder. Pump the brakes only within the normal range of motion you use every day.

BTW...you shouldn't need to bleed brakes after a normal pad/rotor change.

Did you line the cross in the brake piston to the peg on the inboard brake pad?

Are the pads properly lubed at the ears where they touch the caliper hardware? Do they slide easily?

Do your caliper pins move freely?

New rotors ship with oil all over them. Did you spray them with brake cleaner to get rid of the oil film before installing them?

Google and go over the basics of a brake job. Or...end your misery and just take it to a professional.

Last edited by B serious; 06-12-2018 at 10:40 AM.
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Old 06-12-2018, 08:05 PM
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Default Re: brake hissing sound

I have correctly did all the things listed above. it is not my first time to perform a brake job, all brake parts move freely and are cleaned and lubed. i will perform another brake system bleed like you said without pushing the pedal all the way down.
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Old 06-13-2018, 12:49 AM
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Default Re: brake hissing sound

it's actually best to use a vacuum pump to pull the fluid at the caliper, only need one person

I'm sure there are numerous howto's on youtube
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Old 06-13-2018, 08:50 AM
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Default Re: brake hissing sound

Iím not having a problem bleeding the brakes. I believe the brake booster might have an problem.
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Old 06-13-2018, 10:16 AM
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Default Re: brake hissing sound

A booster issue would be indicated by a hard pedal with under-effective brakes. Like how the brakes feel when the car is turned off and you pump the pedal a few times.

A booster gives power assist to the brakes.


As mentioned before...You shouldn't have needed to bleed the brakes in the first place. You were just replacing rotors and pads.

I assume you know that newly serviced brakes require pumping the pedal to take up all the extra travel initially?

Did you do that? Or did you just dive into a brake bleed for no reason?

Difficult to diagnose now, unfortunately....
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Old 06-13-2018, 10:27 AM
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Default Re: brake hissing sound

Originally Posted by B serious View Post
A booster issue would be indicated by a hard pedal with under-effective brakes. Like how the brakes feel when the car is turned off and you pump the pedal a few times.

A booster gives power assist to the brakes.


As mentioned before...You shouldn't have needed to bleed the brakes in the first place. You were just replacing rotors and pads.

I assume you know that newly serviced brakes require pumping the pedal to take up all the extra travel initially?

Did you do that? Or did you just dive into a brake bleed for no reason?

Difficult to diagnose now, unfortunately....
Brake booster damage doesn't always mean a stiff pedal, had a customer in my shop with an 07 element that had a hole in the booster. Pedal felt normal, but hissed vaccum leak when you pressed on the brakes.
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Old 06-13-2018, 05:48 PM
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Default Re: brake hissing sound

valid.

But...I don't know if this is the hiss he is talking about.

It might just be the normal hiss one gets when hitting the pedal in a car with vacuum assist. Not a constant hiss.

He is also not complaining about idle issues from intake manifold vacuum loss.

He also just replaced pads and rotors.
So...there's probably a better likelihood that he did something wrong than there is a chance that his booster failed for no reason...coincidentally at the exact moment that he shut his car off to put on pads and rotors.

KnowwhatImean?

His brakes were presumably fine before.

His pedal is also soft and has tons of travel. The opposite symptoms of a leaking booster.

A leaky booster is *possible*, but the chances that there now exists a snake who crawled into the dash and is activated by his brake pedal is also *possible*
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Old 06-13-2018, 08:36 PM
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Default Re: brake hissing sound

Originally Posted by kirlous k View Post
I have recently changed my rear brake pads on my 08 accord, after changing the pads i go to test the car and i find that i have a spongy pedal. So i bleed the brakes using the 2 person method but i still have a spongy pedal, however the brake pedal is soft all the way until it comes close to the floor then it gets hard. when i tried to brake the brakes where hardly grabbing until pressing the pedal almost all the way. I also started to hear a new hissing sound coming from the brake pedal and near the brake master cylinder and brake booster. this makes me having to press the brakes way before i intend to stop.
This actually sounds like you have some air in your master cylinder. How low did the brake fluid reservoir get while you were bleeding the brakes?

Air in the MC would lead to these symptoms and make an air squishing type of noise when you hit the pedal. Not quite the same sort of hiss that you'd get from a vacuum leak but it isn't far off.
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Old 06-14-2018, 10:17 AM
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Default Re: brake hissing sound

Originally Posted by B serious View Post
A booster issue would be indicated by a hard pedal with under-effective brakes. Like how the brakes feel when the car is turned off and you pump the pedal a few times.

A booster gives power assist to the brakes.


As mentioned before...You shouldn't have needed to bleed the brakes in the first place. You were just replacing rotors and pads.

I assume you know that newly serviced brakes require pumping the pedal to take up all the extra travel initially?

Did you do that? Or did you just dive into a brake bleed for no reason?

Difficult to diagnose now, unfortunately....
yes i have pumped the pedal correctly and the new pads are broken in now.
i have bled the brakes because that would be the first thing to check when the brake pedal is soft.It did not hurt to bleed the brakes.
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Old 06-14-2018, 10:18 AM
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Default Re: brake hissing sound

Originally Posted by boxedfox View Post
This actually sounds like you have some air in your master cylinder. How low did the brake fluid reservoir get while you were bleeding the brakes?

Air in the MC would lead to these symptoms and make an air squishing type of noise when you hit the pedal. Not quite the same sort of hiss that you'd get from a vacuum leak but it isn't far off.
i have always topped off the master cylinder after each caliper bleed, it was almost always full.
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Old 06-16-2018, 05:18 PM
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Default Re: brake hissing sound

find out where the hiss is coming from and go from there
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