Brake Issue Help?

[YOTALUVR]

Hello, micro question for the mechanically inclined a I have a 2000 Tacoma Xtra cab 4x4 automatic, my brakes fail while at a stop light. Basically if I'm driving it she stops on a dime but if I come to a stop it starts to slowly sink then sink some more and then just fails completely. I've checked the brake lines and they are not leaking I have 4 brand new brakes/rotors on all 4 tires. Literally about 400 miles on them. I need any input or if you guys may know what's wrong.

 

[Duke562]

I'm no mechanic just a wild guess
Symptoms of a Bad or Failing Vacuum Brake Booster Check Valve
Common signs include the brake pedal being difficult to engage, feeling spongy, or not working at all.


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[Sculsz]

I'm no mechanic just a wild guess
Symptoms of a Bad or Failing Vacuum Brake Booster Check Valve
Common signs include the brake pedal being difficult to engage, feeling spongy, or not working at all.


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I would have to agree!!

 

[4xt4r]

Hello, micro question for the mechanically inclined a I have a 2000 Tacoma Xtra cab 4x4 automatic, my brakes fail while at a stop light. Basically if I'm driving it she stops on a dime but if I come to a stop it starts to slowly sink then sink some more and then just fails completely. I've checked the brake lines and they are not leaking I have 4 brand new brakes/rotors on all 4 tires. Literally about 400 miles on them. I need any input or if you guys may know what's wrong.

My vote is a failing Master cylinder.

 

[DMV4runner]

My vote is a failing Master cylinder.

I second this vote.

When you had your brakes done just a short time ago, back pressure was probably applied on the master cylinder when the calibers were compressed to allow new pads. Was the cap pulled on the MC to allow back filling? If not done properly or carefully, it can ruin your seals in the master cylinder.
Or it could just be a coincidence that it occurred right after your brake job.

 

[YOTALUVR]

I second this vote.

When you had your brakes done just a short time ago, back pressure was probably applied on the master cylinder when the calibers were compressed to allow new pads. Was the cap pulled on the MC to allow back filling? If not done properly or carefully, it can ruin your seals in the master cylinder.
Or it could just be a coincidence that it occurred right after your brake job.

Toyota did all the work, so i have no idea. How easy is it to replace?

 

[Morphyne]

I second this vote.

When you had your brakes done just a short time ago, back pressure was probably applied on the master cylinder when the calibers were compressed to allow new pads. Was the cap pulled on the MC to allow back filling? If not done properly or carefully, it can ruin your seals in the master cylinder.
Or it could just be a coincidence that it occurred right after your brake job.

This is exactly how my buddy ruined his MC in his caravan . It was super easy to replace.