[smukherjee]

My new I20 (300 kms on the ODO) sometimes makes a 'swoosh' sound when I press the brakes a little harder than normal. It seems like air being pushed out - but that could be a huge worry for a new car right? Never noticed any brake fluid leakage or anything amiss on the control panel. Help

[saket77]

Originally Posted by smukherjee

My new I20 (300 kms on the ODO) sometimes makes a 'swoosh' sound when I press the brakes a little harder than normal. It seems like air being pushed out - but that could be a huge worry for a new car right? Never noticed any brake fluid leakage or anything amiss on the control panel. Help

That is the brake booster doing its job. Should be hardly audible at driving speeds, easily noticeable on a standing car. Nothing to worry about.

[smukherjee]

Originally Posted by saket77

That is the brake booster doing its job. Should be hardly audible at driving speeds, easily noticeable on a standing car. Nothing to worry about.

I am planning to take the car to Ooty (from Bangalore) on the Oct 1st long weekend - was really worried about driving with iffy brakes on the ghats.

[sagarpadaki]

Originally Posted by smukherjee

My new I20 (300 kms on the ODO) sometimes makes a 'swoosh' sound when I press the brakes a little harder than normal. It seems like air being pushed out - but that could be a huge worry for a new car right? Never noticed any brake fluid leakage or anything amiss on the control panel. Help

First thing, i20 does not have Air brakes. So there is no air to be pushed out.

Second thing, are you getting this swooosh sound if you decelerate rapidly from high speed(Above 50 kmph)? Not slamming on the brake kind but smooth progressive increase in pedal pressure at high speeds. If yes, this is normal and i have experienced this in the car

[TB16]

Originally Posted by smukherjee

My new I20 (300 kms on the ODO) sometimes makes a 'swoosh' sound when I press the brakes a little harder than normal. It seems like air being pushed out - but that could be a huge worry for a new car right? Never noticed any brake fluid leakage or anything amiss on the control panel. Help

Not to worry. That sound comes from my i20 aswell (4 mnths old).
Since you've also noticed this, I'll ask my service advisor about this when I'll visit HASS sometime next week. Im guessing it will be a normal thing. Will keep you posted.

[Jeroen]

Do you get the swoosh sound only when you are pressing the pedal? So once you keep the pedal down and are braking it goes away? So directly and only proportional to the brake pedal movement?

If so, it could be just a bit of mechanical sound coming from the master cilinder as you move the plunger which is attached to the brake pedal via some linkages. The plunger displaces the hydraulic fluid and the seals ensure a tight fit. Plunger movement inside the master cilinder and displacement of hydraulic liquid might lead to these swoosh sounds. Also, there might be some rubber bellows at back of the master cilinder where the plunger goes in. When pushing/releasing the brake pedal these bellows expand/crimp. Sometimes you hear a bit of air being sucked in or blown out. The bellow is only to prevent dirt built up on and near the plunger and seals.

Any of the above, nothing to worry about.

Jeroen

[saket77]

Originally Posted by sagarpadaki

First thing, i20 does not have Air brakes. So there is no air to be pushed out.

Sagar, all modern cars come with brake boosters which do suck in air to replace the vacuum in the booster. This is vacuum assistance. This helps cut the effort in pressing brake pedal by the driver.
So, the sound is not of being air 'pushed out'. It is in fact the sound of air getting sucked in.

Regards,
Saket

[Jeroen]

Originally Posted by saket77

So, the sound is not of being air 'pushed out'. It is in fact the sound of air getting sucked in.

If its the booster, it's both. One side is vacuum, the other side is open to vent to the air. So depending on whether you step on the brake pedal or release the brake pedal, air gets sucked in, or air gets expelled respectively.

Now, open up your hood, leave the engine and ignition of and push on the brake pedal a few times. then try with the engine of. The difference being having vacuum or not having vacuum and depleting the vacuum with a few pedal stroke as the engine or ignition is switched off.

Is the sound really coming from the booster?

Could be, but it might be other causes as per my earlier post

Jeroen

[saket77]

Originally Posted by Jeroen

If its the booster, it's both. One side is vacuum, the other side is open to vent to the air. So depending on whether you step on the brake pedal or release the brake pedal, air gets sucked in, or air gets expelled respectively.

Jeroen, I did not get the quoted part of your post. My understanding is that one end of the brake booster is connected to engine vacuum which keeps creating a vacuum in the booster while the engine is running. The other end draws in air when the pedal is pressed which replaces the vacuum. This helps make the pedal lighter in operation. I believe there is no air pushed out from any end as the air that gets from one end is cleared by the vacuum created at the engine end.

Regards,
Saket

[Jeroen]

Originally Posted by saket77

Jeroen, I did not get the quoted part of your post. My understanding is that one end of the brake booster is connected to engine vacuum which keeps creating a vacuum in the booster while the engine is running. The other end draws in air when the pedal is pressed which replaces the vacuum. This helps make the pedal lighter in operation. I believe there is no air pushed out from any end as the air that gets from one end is cleared by the vacuum created at the engine end.

Hi,

there are all sort of brake boosters out there, but lets start with the basic most simple form of a car brake booster. I explain and I also found quite a nice article with some good pictures hopefully explaining it in some more detail.

A brake boost is essentially a cilinder with a flexible membrane in the middle. One side of the membrane is attached towards the brake pedal, the other side toward the plunger. By creating pressure differential over the membrame it assist the force from the brake pedal.

So it needs a pressure differential, otherwise it would not work. On the side of the plunger it is connected, via a check valve to the engine intake manifold or vacuumpump (e.g. on a diesel engine). So on one side of the membrame a vacuum is created and maintained by either the engine intake vacuum or the vacuum pump. The other side of the membrame is open to the atmosphere.

When you push the brake pedal you push the plunger in. Its assisted by the vacuum on the one side of the membrame. On the other side of the membrame, as this is open to the atmoshere air actually is "sucked" in if you like because of the displacement of membrame. Conversely, when you let go of the brake the membrame returns to it's original position and that menas the air that was 'sucked in" is expelled again.

So the vacuum is not replaced as you said/thought, it's maintained all the time. The vacuum side is completley seperated from the other side which is open to the air. If the membrame develops a little tear you loosed the vacuum and that results in the booster not working properly and you feel that in having to press the brake pedel more to get the same braking response.

Have a look at this:

http://auto.howstuffworks.com/auto-p...wer-brake1.htm

For those of us are more visually orientated here is a nice youtube as well. Actually this guys adds some additional details, but the principle remains the same. You'll notice that he at one points says" the (atmospheric) air rushes in.

https://www.youtube.com/watch?v=LThrL8Jjsgc

To birng it back to topic on where sounds might come from; obviously not from the vacuum. It's not a very high vacuum, but still it has fewer air molecule than the other side that is open and vents to the air. So, if you hear noises, my experience is usually more along the more mechanical sounds as origin that air, but still, as you will see/understand by now I hope air does go in and out of the booster.

Let me know if this helps you in your understanding of how the booster works.

Jeroen

[saket77]

Originally Posted by Jeroen

So on one side of the membrame a vacuum is created and maintained by either the engine intake vacuum or the vacuum pump. The other side of the membrame is open to the atmosphere.

This quoted text was all I needed to understand.

Thanks for the elaboration. Really appreciate it.

Regards,
Saket

[TorquePeedo]

Reopening the thread after a long while. I recently bought a preowned 2009 Honda City ivtech S-AT. It is having a strange noise when slight brake is applied or when it slows down to a halt. I have got the original honda brake pads replaced and also tried replacing the rotor disc but the sound is still there. One strange thing is that if I jack up the tires and try accelerating and apply slight brakes the sound is not there. Tried visiting honda workshop but they were not able to find a solution and are now suggesting replacing the hub

The link below showcases the kind of sound I am talking about although it is not my video

https://www.youtube.com/watch?v=-WFcBNcMBMQ

Any help would be appreciated

[silverado]

Originally Posted by Jaggu

Were the brakes by chance wet, due to driving in rain or car washing? If so a wet pad can cause grunting noise sometimes while braking hard, till it dries.

Exactly my case. I had Baleno pressure washed today and the noise immediately started after that.

It was loud grinding noise when I applied normal braking pressure.
So scary as if someone had placed a stone between caliper and disc.

It is this thread and this reply from Jaggu which saved me a visit to Maruti.

[gopaneel]

Originally Posted by kaushik_s

Hi All,
Need some help here. Recently have been facing a very strange kind of problem. While braking at very low speed (10-20kmph) if I brake then I'm hearing strange grinding noise. The noise is like there is some stretch in some metallic parts somewhere at the brakes. This noise is more pronounced when at a downward incline (specially at my basement parking). While reversing I'm not able to hear any noise while braking. I've a doubt that it may be related to suspension but it can be the brakes also. I vaguely remember that this problem started after the brake-pad change but I can't tell it for sure. Shown the problem to service centers but are yet not able to find the problem.
Regards,

I have a similar noise while braking in my Glanza which has done 1000kms. The scenarios it occurs are exactly same as mentioned by the OP. However, it's not a very coarse noise. I did take it to the service center today. But the Toyota technician could not diagnose/fix it even after taking out the wheels and cleaning it. Also, the guy admitted they are not as familiar with Maruti manufactured cars as they are with the Toyota manufactured cars. He also mentioned that Toyota parts are better quality than the Maruti. So they are not sure if this noise is common to the Balenos.

I saw this thread now. I see problems mentioning greasing and the caliper pins. Could these be applicable to a 1000km car?

I did see an issue related to brake noise on the Baleno. Is this the same?

[drsachin]

I recently underwent service at a Gomechanic workshop(JMS automobiles, Sahibabad). Since it was a lockdown, the ease of sitting at home and booking through app sounded good. The Hyundai ASS were closed in april in my area. While servicing they informed that my rear brake pads needed replacement. My car had run 75000kms and they were running on original pads. They did send photos of both front and rear brake pads. The rear brake pads were indeed very thin. The front brake pads were as good as new.
They changed rear brake pads to a company named "Compo Advics". I was given 20000kms warranty on these brake pads. Those brake pads worked ok for around around 2500kms but after that they started giving me issues. At slow speeds there was a whistling sounds from rear tyres. I stopped the car and checked on brakes and noticed that my rear brake rotors were as hot as a furnace, while the front rotors were just warm. There was a burning smell near rear brake pads.
I complained at Gomechanic ,and they suggested to bring the car back to workshop. They removed the brake pads and noticed some stray metal wires at some places on the brake pads. Later they changed these brake pads to new one from another company called "Allied Nippon". Now my car has run another 3000kms and no such issues.

I regularly check my brake pads now for damage and rotors for heating issues. I still notice that rear rotors are hotter compared to front ones but not furnace hot as before.

Few questions from fellow Team bhpians.
1. Is it normal for a car to have such differential front and rear brake pad wear. As per mechanic my front brake pads is as good as new. He thought I might have replaced them at last service. Even my rotors show uneven wear. Front rotors are as good as new, while rear ones show appreciable wear in the form of lines.

2. Should I continue with this new brake pads from "allied Nippon" or should I get them changed to some branded ones like Bosch, Roulunds, IGB or OEM. OEM ones are indeed expensive at Rs6000. Rest all are available for around 700 to 1000.