Adding my experience with this issue.
Context: One day, the firewall just started making this squeal noise. Every 5 seconds. It was constant. Had to do my investigation on this system and issue since I am new to Toyota. Ended up trying a temporary fix that worked for a few months. Issue was from the brake master area.
Removed the accumulator and replaced the pipe, spring, and o-ring. This solved for the squeal.
The sound came back, so I gave in and found a brake pump part brand new for $700ish. My plan was to swap just this part rather than paying $1800 for the whole Brake Master Assy itself.
I followed a thread on here for removal of brake master assy that helped a lot. I found out that the brake system had been worked on previously due to the rounded brake fittings to the master cylinder. I had to buy a very specific flare nut wrench brand “SK Tool”. Since this tool gets great reviews for fitment to nut from Jeep owners. The harbor freight ones were too sloppy.
Even more evidence of previous work was the 4 nuts securing the assy to the firewall. The top right nut was missing. Well damn that sucks lol. Luckily, I pulled back the front carpet and there it was. A lazy tech just left it there.
Once I was able to remove the four brake fittings, three 12v connectors, 4 nuts and clevis brake pin and clip, the assy came out with some finesse.
Swapping over the new hydroboost pump is straight forward. I also purchased a new brake line from the hydroboost pump to master cylinder (red wrapped brake line). The old one was super rusty.
Be very careful when swapping over the +/- terminals for the pump as the Philips head that secures the terminals is easy to strip.
Once I swapped the pump over, I installed everything back (ensure you hand start your brake fittings) and topped off the brake fluid. I turned the key to on and heard the pump prime. No more squeal noise.
But once I stepped on the pedal to move the car to another location, it squealed again. At this point, it came back and was constant again. I decided I would have to buy a whole brake assy after this.
I was not too happy and told my wife to help me with bleeding the brakes. We bled the brakes in the rear and found some chunks of rust in the lines. The squeal went away after this. Once I bled the rears, and then fronts, the squeal is no longer there, and the pedal feels great. I am not sure if the clogged lines were the culprit of the constant activation of the pump, or maybe this is a temporary fix. Either way, if I need a new brake master assy, I know the process in changing it out now.
Context: One day, the firewall just started making this squeal noise. Every 5 seconds. It was constant. Had to do my investigation on this system and issue since I am new to Toyota. Ended up trying a temporary fix that worked for a few months. Issue was from the brake master area.
Removed the accumulator and replaced the pipe, spring, and o-ring. This solved for the squeal.
The sound came back, so I gave in and found a brake pump part brand new for $700ish. My plan was to swap just this part rather than paying $1800 for the whole Brake Master Assy itself.
I followed a thread on here for removal of brake master assy that helped a lot. I found out that the brake system had been worked on previously due to the rounded brake fittings to the master cylinder. I had to buy a very specific flare nut wrench brand “SK Tool”. Since this tool gets great reviews for fitment to nut from Jeep owners. The harbor freight ones were too sloppy.
Even more evidence of previous work was the 4 nuts securing the assy to the firewall. The top right nut was missing. Well damn that sucks lol. Luckily, I pulled back the front carpet and there it was. A lazy tech just left it there.
Once I was able to remove the four brake fittings, three 12v connectors, 4 nuts and clevis brake pin and clip, the assy came out with some finesse.
Swapping over the new hydroboost pump is straight forward. I also purchased a new brake line from the hydroboost pump to master cylinder (red wrapped brake line). The old one was super rusty.
Be very careful when swapping over the +/- terminals for the pump as the Philips head that secures the terminals is easy to strip.
Once I swapped the pump over, I installed everything back (ensure you hand start your brake fittings) and topped off the brake fluid. I turned the key to on and heard the pump prime. No more squeal noise.
But once I stepped on the pedal to move the car to another location, it squealed again. At this point, it came back and was constant again. I decided I would have to buy a whole brake assy after this.
I was not too happy and told my wife to help me with bleeding the brakes. We bled the brakes in the rear and found some chunks of rust in the lines. The squeal went away after this. Once I bled the rears, and then fronts, the squeal is no longer there, and the pedal feels great. I am not sure if the clogged lines were the culprit of the constant activation of the pump, or maybe this is a temporary fix. Either way, if I need a new brake master assy, I know the process in changing it out now.
