It needs to be lubricated where the pedal hangs off of the pivot point.
The brake pedal has a hinge or pivot pin, give it a shot of lubricant,should stop squeaking.
dry brake shoe/pad operating arm on rear brakes
manualy lift brake pedal to see if they go out. if so check spring at pedal
Pressure is released from the hydraulic system and brake pistons relax.
Why do brake pads squeak after replacing pads?
Push the brake pedal to released.
Look under dash near brake pedal assembly for a damaged wire grounding when pedal is released. Repair and tape it out of the way.
When Exhaust brake is on squeak noise comes from the engine?"
Breaks will often squeak when they are wet, such as after a heavy rain, on a humid day, or on a foggy morning. The water prevents the pads from properly grabbing the rotors. This causes the squealing noise.
The power brake booster is bad.