LX 570 hissing sound?

[TJnoob]

Hey everyone, I just purchased a 2008 LX 570 and noticed there is a cyclical hissing sound. It’s sounds a bit like Darth Vader. I can also feel it in the brake pedal. Braking seems normal, although the pedal depresses an inch before the brakes actually start to engage. Any help is appreciated to get me pointed in the right direction. Cheers!

 

[tbisaacs]

Totally normal - there is a "whoosh" sound when hitting the brake pedal when hitting the pedal in my truck too.

 

[GOLIGHTLY]

Hey everyone, I just purchased a 2008 LX 570 and noticed there is a cyclical hissing sound. It’s sounds a bit like Darth Vader. I can also feel it in the brake pedal. Braking seems normal, although the pedal depresses an inch before the brakes actually start to engage. Any help is appreciated to get me pointed in the right direction. Cheers!

Second what @tbisaacs said. Same on my ‘10. For whatever that’s worth.

 

[TJnoob]

So, the sound isn’t happening when I press the brake pedal. It’s actually a constant repeating sound that’s obvious when I’m cruising around with the radio off. It sounds like the truck is breathing. It was just odd that I can feel it in the brake pedal while I’m at a stop.

 

[TeCKis300]

The sound is familiar and is related to the brake booster. The 200-series uses an electronic brake booster. Usually the sound is associated with actuation of the brakes and it is a breathing type sound. Can also be subtly felt in the pedal. This is common to many Toyota/Lexus models that utilize newer electronic brake boosters.

How often are you getting the sound? It's noticeable with a new car especially if hyper focused on new noises. I don't notice it anymore perhaps also related to my AT tires.

It is possible that the master brake cylinder/booster is internally leaking down? It's the sound is the booster keeping fluid pressure up.

 

[TJnoob]

The sound is familiar and is related to the brake booster. The 200-series uses an electronic brake booster. Usually the sound is associated with actuation of the brakes and it is a breathing type sound. Can also be subtly felt in the pedal. This is common to many Toyota/Lexus models that utilize newer electronic brake boosters.

How often are you getting the sound? It's noticeable with a new car especially if hyper focused on new noises. I don't notice it anymore perhaps also related to my AT tires.

It is possible that the master brake cylinder/booster is internally leaking down? It's the sound is the booster keeping fluid pressure up.

The sound is constant. I think I’m going to name the truck Darth. I looked up brake booster issues but read that those are typically followed with pump cycling noise which I don’t hear. It seems to drive normally. Brakes fine although I have to anticipate that the pedal goes in one or 2 inches before the brakes engage.

 

[TeCKis300]

Constant doesn't seem normal and probably worth getting it checked out. If you have techstream (high recommended and relatively cheap to get), check to see if you have any codes in the ABS/Traction Control module.

The brake booster is right at the drivers side, top and back of the engine bay, mounted on the firewall. You'll see the brake fluid reservoir. Take off the engine covers and take a listen. Is it making the noise with the ignition on, but engine off? I recall mine is pretty silent.

The brake feel on the 200-series is indeed different from most cars. It has longer travel before engagement and needs relatively more travel to modulate. Rather than the feel of modulating with just pressure in most modern cars. There's lots of threads on this. My opinion is that it is purposely tuned this way to help modulation off-road where things can be very bumpy, and could assist the driver in not braking traction over lose surfaces. Don't mistake that for weak brakes as it's strong when deliberately braking. Just different, and with some seat time, you won't give it a second thought. I noticed it too when I first got the car, especially as I switch between as sports car and this regularly.

 

[TJnoob]

Constant doesn't seem normal and probably worth getting it checked out. If you have techstream (high recommended and relatively cheap to get), check to see if you have any codes in the ABS/Traction Control module.

The brake booster is right at the drivers side, top and back of the engine bay, mounted on the firewall. You'll see the brake fluid reservoir. Take off the engine covers and take a listen. Is it making the noise with the ignition on, but engine off? I recall mine is pretty silent.

The brake feel on the 200-series is indeed different from most cars. It has longer travel before engagement and needs relatively more travel to modulate. Rather than the feel of modulating with just pressure in most modern cars. There's lots of threads on this. My opinion is that it is purposely tuned this way to help modulation off-road where things can be very bumpy, and could assist the driver in not braking traction over lose surfaces. Don't mistake that for weak brakes as it's strong when deliberately braking. Just different, and with some seat time, you won't give it a second thought. I noticed it too when I first got the car, especially as I switch between as sports car and this regularly.

Finally took a look. The brake booster pump is definitely where the noise is coming from. It cycles only while the engine is running. When the car starts up it pumps For about 30 seconds, I assume to create pressure in the lines, but then cycles every 2 seconds. Is this normal or does it indicate a failing part?

 

[ramangain]

How is your brake fluid level? Quality?

When was the last time the brakes were properly bled?

 

[TeCKis300]

Finally took a look. The brake booster pump is definitely where the noise is coming from. It cycles only while the engine is running. When the car starts up it pumps For about 30 seconds, I assume to create pressure in the lines, but then cycles every 2 seconds. Is this normal or does it indicate a failing part?

Just checked against mine.

- 15 seconds initial prime
- 30 seconds pause and another few second prime
- waited 3 minutes with no further priming

Sounds to me like there's an internal leak in the brake booster/accumulator that's a part of the master brake cylinder assembly. Probable it could be air in the system and may be worth trying to bleed the master brake cylinder (which requires techstream).

I actually have a whole master brake cylinder assembly as I replaced mine not too long ago troubleshooting my center diff lock. The Lexus debug manuals where wrong and it turned out to be something within the transfer case. The master brake cylinder assembly is a pretty pricey part but I'm willing to let it go for pretty cheap if you want to IM me.

 

[EverywhereBear]

I used to get periodic hissing from my 08 LX, something besides the brake. Was the AC system. I had a small leak in the rear AC line. The hissing went away when recharged the AC system.