Replaced front brakes, now 'clap'

[Project23D]

 

Last year I replaced my front brakes, to which I made  youtube video on how to replace/repair the wear sensor. I noticed the pads had un-even, curved wear. Watch the video on youtube. My username is the same as the one I use on here.

I've changed brake pads on several other cars, and have never had any issue with following directions for each car.. which they are all just about the same when it comes to carefully and very slowly pressing the piston back in as I usually keep the bleeder valve closed.

Both front curb and road side pad sets were changed. Rotors were inspected, found to have lots of life left, and according to service records, changed out at 99k miles.

Three times since I have bleed All of the brakes, starting from the rear to front, following closely to the directions of lexls.com and the issue still remains.

 

[this particular issue]

the best way I can describe the noise I hear is clapping coming from the front brakes...

What I do is the following: I get in the car, start the engine. Step on the brake pedal, select reverse gear. I let off the brakes slightly, and squeaking(still!) as the car rolls backwards until I press harder on the brakes again to stop. And when I do that that is when I hear what sounds to be the front brakes clapping...

Then I change the gear selector to drive, and go forward. When I get to the first stop sign in the direction I am going, I'll step on the brakes again.  They'll clap. And they do this every time I step on the brake to slow or  comes to a stop. Doesn't matter what speed, but the clapping does NOT occur on a hard/fast brake pedal press.

I find myself now pumping the brakes lightly every time just before I really want to apply pressure to slow down or stop so the damn embarrassing clapping does not occur... as this issue has been kicking my !Removed!!

I've noticed for a while now, when the engine is running, a hissing can be heard from where the master cylinder meets the brake booster. The hissing noise has been pin pointed. See the image with my finger. I cannot find if this is normal for this car or if there is an issue. I'm pretty sure I detected the noise when I got the car, and there were no issues with the brakes, and doing my usual thing of opening the hood, gawking at the running engine, and seeing how the silly thing works when I first get a car, haha!

ALSO, I am not sure when this started, or just really when I noticed it, but when I press on the brake pedal, I can hear a hissing noise inside the cab coming from under the dash. This occurs every time I press on the brake pedal.

Before I perform the band-aid fix of applying silicon sealant to where the master cylinder meets the brake booster, as funds are not available for a full fix yet, I want to make sure this is normal for this car..  Although none of my other cars have the hissing noises and the transmission seems to shift funny at random times, but I don't know if the transmission uses vacuum for anything AND this leak is a part of THAT issue.

 

[Exhaustgases]

And most important what year of LS400?

[billydpowell]

his post says 1998, my 99 does not hiss.... 

[sha4000]

I've never heard the brake booster hissing.

[Lexus_DK]

I believe there is a big rubber o-ring on the master cylinder where it mates/seals to the brake booster. It might of rollled off when someone tried installing a new MC or that o-ring is worn. Trying removing the 2 nuts holding the master cylinder and inspect. If and when you do replace that o-ring, make sure you lube it with silicone grease.

[Lexus_DK]

And no, it shouldn't be making that hissing noise. 

[Project23D]

I am glad you said that it shouldn't hiss. I came across a post with a part number for this o-ring which does not seem to be available perhaps either because it is not, or the part number is/was wrong. Or, the o-ring only comes with a either a new master cylinder or brake booster.

After cleaning with 90% alcohol, I put a generous amount of silicon sealant right where the mastery cylinder meets the brake booster from what could be considered from 4 o'clock to 9 o'clock.

I let it sit overnight and now there is not any more hissing.

I am certain that because I let this problem manifest for so long, all of the brakes have to be replaced )-:

[Lexus_DK]

Here's what the o-ring should look like. I just recently replace a master cylinder on a 2008 es300.

 

 

[M.Yasir]

It appears that you have two separate issues

1.) Hissing sound while pressing the brake pedal

2.) Clapping noise while breaking

I am not sure of how this hissing noise is affecting you except you are able to hear, are you noticing any vaccum leak while pressing your brake pedal? is it becoming soft?

Clapping noise, what i understand is the sound is metallic clapping between the rotor and the brake pad, double check the installation or take help from a friend so that he can observe from outside that actually what is happening when you are applying brakes, maybe there is a problem in the caliper, or you missed something during the brake pads replacement