1999 LX470 Strange Noise Behind Dash (1 Viewer)

[ffl3883]

Hello,

i have a 1999 LX470. I noticed there is strange noise (sounds like servo motor or kind of screwing sound) when I first turn on key to light up the dash also when I press brake several times. It also happens frequently during driving when I press brake pedal several time, like in heavy traffic. Brake still functioning.
Here is a YouTube link.



you might need to put on headphone to hear the noise clearly in the YouTube video. Just wondering what the problem is and any thoughts and guidance are appreciated.

Regards

Felix

 

[YodatheLC]

Sounds like it could be brake booster

 

[LXander]

Sounds like my auto height leveling on my 98.

 

[gil12]

I vote for the brake booster. If the truck hasn't been driven for a few hours, the electric booster motor will run for 30 to 40 seconds until the pressure gets up to value. Listen to the master cylinder when you first turn the key.

 

[ffl3883]

I vote for the brake booster. If the truck hasn't been driven for a few hours, the electric booster motor will run for 30 to 40 seconds until the pressure gets up to value. Listen to the master cylinder when you first turn the key.

So does the fact that it turns on frequently after braking suggest I lost hydraulic pressure in the master cylinder? What do you suggest to check on the master cylinder? Thanks

 

[ffl3883]

Sounds like it could be brake booster

Does it turn on often in your vehicle ? What would you suggest to check for

 

[2001LC]

Sounds normal. Quick test: Key off, depress brake peddle 40 times, force becomes light when pressure is released. Turn on ignition switch (ON). Pump should stop after approx. 30 to 40 sec.

 

[ffl3883]

Thanks for the reply. The noise definitely comes from master cylinder assembly. The brown canister (brake booster?) shakes when the noise come on.

 

[YodatheLC]

Does it turn on often in your vehicle ? What would you suggest to check for

It happens every time I turn the truck on, and frequently while applying brakes. The only need for a fix is when it fails. You will know because you will not have any stopping power shortly after it fails. Price to fix for PM is upwards of 2-2.5k. I'll get everything out of mine before I drop that cash. That part is very expensive.

 

[ffl3883]

It happens every time I turn the truck on, and frequently while applying brakes. The only need for a fix is when it fails. You will know because you will not have any stopping power shortly after it fails. Price to fix for PM is upwards of 2-2.5k. I'll get everything out of mine before I drop that cash. That part is very expensive.

Thanks for the information. They are very useful. I can hear the motor working in the booster whenever I press brake padel 4-5 times. I am wondering what are the symptoms of a failing booster ?

 

[YodatheLC]

Thanks for the information. They are very useful. I can hear the motor working in the booster whenever I press brake padel 4-5 times. I am wondering what are the symptoms of a failing booster ?

there is a thread on the specifics of what to look for when a booster is failing. From what I can remember there is very little evidence it's going out. Maybe a change in the noise the booster makes when building pressure, going to something not so mechanical. But for the most part no warning, and then a loss brakes, not completely but from what I have heard on here the peddle will travel straight to the floor.

 

[ffl3883]

there is a thread on the specifics of what to look for when a booster is failing. From what I can remember there is very little evidence it's going out. Maybe a change in the noise the booster makes when building pressure, going to something not so mechanical. But for the most part no warning, and then a loss brakes, not completely but from what I have heard on here the peddle will travel straight to the floor.

Sounds very dangerous if it happens On the highway. I was told that the ABS light and some other indicator would light up on the dash if brake fails. Is there a safe practice procedure in the event of a booster failure ?

 

[YodatheLC]

Sounds very dangerous if it happens On the highway. I was told that the ABS light and some other indicator would light up on the dash if brake fails. Is there a safe practice procedure in the event of a booster failure ?

Down shift manually, use emergency brake carefully