2009 Prius noise behind dashboard - percolator sound

I have a 2009 Prius with 100k miles and recently I have been hearing a percolator type sound (or bubbling sound) coming from behind the dashboard (and under the car hood). I don't know what is causing this but when I went to the dealership they wanted to charge me $100 just to diagnose it. I thought maybe someone here has experienced the same noise and figured out the cause. I did a video that pinpoints the area from where the sound is coming from and you can hear the noise (percolator sound). However, I can't upload it-is there anyway to upload it so you all can hear it?? Or if anyone already knows the cause please let me know, I would appreciate it! thanks

 

I uploaded the video (with noise) to youtube

 

No work has been done on the cooling system or anything else. The only thing I've done to the car is regular oil changes, cabin and engine filter changes, alignments, and tire rotations. Two days ago, I had the rear brake cleaned and aligned. Also, all my fluids were topped (per tech guy). However, the noise started before taking it to the dealer. Unfortunately, when I took it to the dealer it wasn't making the noise. The noise comes and goes...could be days before I hear it and it only happens when the car is on. Once off the car is off the noise stops.

 

I don’t have any CD’s in there. The noise is coming from under the hood just behind the dashboard.

I don’t know if they balanced the rear break, i’ll ask.

 

Hi All, I took my car to the Toyota dealer and they did a diagnostic test. They gave me a written estimate for replacing the Auxiliary Battery ($339.95) and Brake Actuator ($2359.95)... and this is what they wrote in the remarks:

"Confirmed knocking noise coming from brake actuator. Electrical system diagnostic conducted and multiple low voltage DTC's are present. Notified customer that knocking noise may be due to low voltage to brake actuator. Recommend replacement of auxiliary battery to start and further diagnostic to be conducted afterwards."

I purchased an Auxiliary Battery from Advance Discount Auto Parts for approx. $160.00 and watched a step-by-step youtube video on how to replace the battery. Luckily, my neighbor came over just as I got the cover off the battery and he stepped in to replace it! Took him 20 minutes.. would have taken me 2 hours, lol. After replacing the battery, I took the car for a test drive and the noise behind the dashboard is gone. I'm hoping it was just the battery. I'll let you know if the noise comes back (fingers crossed!)

(I purchased the "AutoCraft Platinum AGM Battery, Group Size S46B24R, 370 CCA")

 

spoke too soon! The noise is back BUT it sounds lower and the "percolator/bubbling" noise is less. I'll wait until the end of the week and report back if the noise increases. The guy at the dealer said that no codes (DTC's) came up for the brake actuator, they just listened to where the noise was coming from and confirmed it that way. They also told me that while it is common for the brake actuator to fail in my 2009 model, the manufacturer would not cover the repair because my VIN number did not show up in the recall, nor did any diagnostic code show up, no warning lights came on in the dashboard and my car is over 10 years old (as of December 2018). Bottom line, if it's the brake actuator the cost is on me. ugh.

I plan on taking my car to a local Prius mechanic (recommended on here) next week for another diagnostic test.

 

I tried changing the air vent selection and the noise was still there. I even turned off my A/C and the noise was still there.