[thoff25]

November 3, 2023 - YouTube

Sometime it happens while I brake. Sometimes after, gets worse going downhill especially with weight in the car. Happens every few miles and the noise ranges from short bursts to long screech. Any thoughts ? 215k on the 2004 4Runner. Gotten worse over the last year. My assumptions point to master brake cylinder and or booster, but it is so loud its weird and I'm lost. Also, braking is fine otherwise, and no codes or dashboard lights. Also, no leaks fluid is maintained at proper level, I have even done brake flush and bleed too. Attached a video.

[ace4aday]

My first thought was the buzzer that goes off when I bleed the rear brakes, but you said you've done that, and I'm assuming it's a different noise. Hard to tell from the video.

[FBELTRAN24]

If this helps any, I own an 07' 4R Limited. Recently had a brake line leak(fixed) that was steady enough to obviously lower the fluid level in the reservoir. When the level became dangerously low/zero, I had a loud, LOUD screeching sound through the speakers until I fixed the leak, and added enough brake fluid to the system/reservoir. The sound immediately stopped, and the VSC/TRAC, and dash lights also immediately shut off.

[thoff25]

Thanks, I will look at the brake lines (I do believe one of them is swollen, I replaced the front 2 to stainless). The fluid reservoir has been staying consistently full, just may be one of the pumps finally dying, but no dash lights. I'm sure they will come soon enough...