Hello Guys,
Im new here, id like to take your opinions about the following:
Stopping on Light Signal, and out of a sudden i got total brake failure and the car moved by itself.
keeping in mind, i just moved the car so no overheating yet.
brembo 4 pistons brakes
no leakage, Brake Fluid is to max.
Dot 4 Brake Fluid in it.

THE PEDAL SANK SO FAST

Thanks in advance

 

If you had brakes, then they suddenly failed you most likely ruptured somewhere, you'll only pump out about as much fluid as you could hold in your hands, the volume in the brake master cylinder is very small so you're not going to see a big puddle or anything like that.

When you completely blow out your brakes it's typically something very obvious like a damaged flexible hose that connects to a brake caliper.

It's also possible your brake master cylinder had some kind of catastrophic failure but I have literally NEVER seen this, even if you entirely blew an o-ring the pedal turns to mush but there's still a little pressure you can build.

It's also possible that maybe your master cylinder linkage suffered some kind of damage, look up under the dash to where the pedal attaches to the master cylinder clevis, work the pedal by hand and see if it's actuating the rod that goes into the master cylinder. Look for any fluid seepage inside the cabin around the actuator rod.

It's also possible that your master cylinder mounting bolts worked loose and that it's no longer attached to the firewall, have someone else work the brake pedal while you look at the master cylinder from the engine bay, also look for any fluid seepage where the master cylinder attaches to the brake booster/firewall.

Your emergency brake is a mechanical cable that attaches to a second set of brake pads inside the rear rotor (it is both an external hydraulic external caliper and a mechanical internal drum brake), it doesn't use hydraulics, your emergency brake will still function if you lose the hydraulic system.

 

If you can't find anything obvious start by replacing the master cylinder. Bench bleed the existing one to see if it will pump fluid. You can also remove the keeper pin and pull out it's piston to see if the o-rings are intact. It's under pressure from a spring so keep that in mind when you disassemble, you can take it apart easily by clamping the BMC in a bench vise so you can use both hands to control the piston on the way out. It's not that much pressure but if you aren't ready for it you'll shoot it about 20 ft and possibly lose the spring.

If the o-ring is broken you can either buy the Nissan rebuild kit for the factory BMC or just source an entirely different unit. Just be sure to bench bleed the brake master cylinder, it's not like the clutch master which you do not bench bleed.