Hissing sound

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Tachycardic

Tachycardic

SILVER Star
Joined
Nov 2, 2019
Threads
44
Messages
670
Location
Oxfordshire
I just noted a hissing/vacuum sound coming from the driver’s footwell. It goes away when pressing on the brakes. It returns when I let go of the brake pedal. Brakes work fine, vehicle drives normally, and there's no CEL. Nothing leaking underneath. Thoughts?
 
Check the hose to the brake booster. Could be loose or leaking and maybe the check valve failed.

Or the booster is getting ready to fail and leaking such that it sucks from the push rod side
 
Could be a Vacuum leak in the power brake booster diaphragm. To test that idea you'd need to disconnect the vacuum hose from the engine to the brake booster. Next apply a vacuum directly to the booster, then check to see if the booster holds that vacuum.
 
Rifleman said:
Could be a Vacuum leak in the power brake booster diaphragm. To test that idea you'd need to disconnect the vacuum hose from the engine to the brake booster. Next apply a vacuum directly to the booster, then check to see if the booster holds that vacuum.
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The hose to the brake booster is in good shape and I just put on new hose clamps as the old ones looked a bit ratty. The check valve is loose. I'm going to replace this first. I'm going to order the following; please let me know if this is correct:

44730-28010 (valve)
90480-24015 (grommet)

Thanks.
 
lol, The first thing to come to mind when you said hissing was Elf


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I just wanted to double check that all I have to do to change the check valve is to pull it out of the booster. Install the grommet to the end of the valve and press fit. Then reconnect the hose?
 
Replaced the check valve and rubber grommet with OEM parts. Still have the hissing sound. Guess it's time to bite the bullet and buy the new brake booster. Dang, every time I get close to being able to afford a roof rack, something pops up...
 
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The old remanufactured brake booster was replaced with a new OEM one and the hissing is gone. Thanks for all your help!

I've saved a bunch of money thanks to this forum and I'm so grateful that I can pretty much find everything I need for my cruiser here. I think it's time to become a silver star member...
 
Tachycardic said:
The old remanufactured brake booster was replaced with a new OEM one and the hissing is gone. Thanks for all your help!

I've saved a bunch of money thanks to this forum and I'm so grateful that I can pretty much find everything I need for my cruiser here. I think it's time to become a silver star member...
Click to expand...
I have a 2014 LX570...any advice on locating the brake booster check valve?
 
Does this help?
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If you don't have a service manual, download one from the Resources section.
 
Wstclx2001 said:
Yup thanks ..found this online awhile ago but can't seem to locate it. I see the fluid resevoir then behind it to the left is what i think is the booster pump but can't see where it connects with manifold...

View attachment 3996073
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Sorry I assumed (without reading) you had an 80. You're posting in the wrong forum.
 
Malleus said:
Does this help?
View attachment 3996063
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Got new pads, rotors and brake fluid. Seems to stop really well in all instances now. Pedal is tiny bit inconsistent from slightly squishy to nice and firm. Symptoms are the brief hissing/squeak when pressing brake pedal but the more troublesome one is when driving for straight long stretches will go to tap break for whatever reason and it will be stuck almost like brake pedal is rusted or something. Tap it with more force but don't have to mash it and it operates normally.

My findings:

1. Makes the famous buzzing sound that triggers a lot of people on here

2. When releasing brake pedal bubbles can be seen in MC fluid resevoir.

Go ahead, tell me i have 4k repair bill in my future lol
 
Malleus said:
NP. FWIW I don't think there is a brake booster on your truck. I could be wrong...
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Ok you're the man thanks Malleus. Wild goose chase looking for parts on Lexus websites only to find my year (2014 570) doesn't fit them when i get to the fitment section. This would confirm your suspicions.
 
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