Brakes are locking all four corners!

[di-devol]

Hi. My brakes are breaking.

Changed master, bled everything, new oem check valve, booster 'checked out'.

Brakes operate normally for the first 5 mins or so, then slowly but surely the brakes start to grab, with more pressure building until the car can barely move. At this point, the brakes will start smoking(all 4 corners).

I've seen calipers get stuck but usually only one, never seen all 4 lol.

Only thing that's left is the booster correct?

Thanks in advance!

Edit: sorry I thought this was in tech, not engine tech.

[bfellini]

Sounds like the push rod between the booster and master cylinder is engaging the master slightly and dragging the brakes. As you use the brakes the booster is building vacuum and adding more assist.

Double check that push rod is properly seated, and either exchange the master, or you can play with o-rings (where the master interfaces the booster to maintain the booster sealing) and shims (between where the master bolts to the booster) to space out the master from the booster to eliminate the issue

[TheRealSy90]

The brake master is not releasing all the way to the point where it releases the fluid pressure. This is due to either the adjustment at the brake pedal, or something causing the brake pedal to no longer return all the way up when you let off of it.
I had this same exact issue on my car and after replacing every single component of the brakes, come to find out it was due to me replacing the grommet in the brake pedal lever with a bolt to hit the brake light switch. The bolt had started to back out, and the brake pedal was not coming all the way up.

[di-devol]

I checked the adjustment rod and I gave it a little free play, brakes still build up pressure. I'll try a booster and check back.

[di-devol]

For anyone ever searching:

New booster fixed the issue, brakes need to be re-bled, but that was it.