The final reason for a brake pedal to go to the floor is failing axle bearing.
2004 gmc sierra brake pedal goes to floor.
Truck brakes were fine.
Does the pedal go to the floor with pressure on the pedal if so master cylinder.
Pumping does not bring it up.
The abs kicked in then the pedal dropped to the floor.
1 leak from brake line or brake caliper.
I can still stop.
Bleed the rest of the system starting at the right rear and move to the left rear then right front and finally left front.
I took the truck on a 30 minute drive the other day and on the way back home my brake light came on and the pedal goes almost to the floor.
With truck running pump the brake pedal several times and hold pressure on pedal after third pump.
System was only bled after the soggy pedal was found.
It s important to not pump the pedal when doing the one part of the bleeding.
If the pedal is hard to push then maybe booster.
Was in a panic stop.
Added front pads and pushed pucks back then went soggy on the pedal.
Technically there are two main causes that would make the brake pedal sink all the way to the floor.
Pedal offers some resistance but can be forced to the floor.
I stopped just inches from the other car.
2000 gmc sierra 5 3 vacuum booster i just had the same thing.
I looked all around the truck for leaks from brake fluid there is none and the brake resiviour sorry for the spelling is still full.
If you still have a low pedal clamp off the 3 flex lines and see if the pedal gets better.
Axle bearings hold the brake rotor true without play while they both rotate.
Rear system is in check and adjusted properly.
If this bearing goes bad it will allow the brake rotor it move back and fourth which pushes the caliper piston back into the caliper creating an air gap.
Reasons your brake pedal goes to the floor.
One of the reasons is the brake system loses pressure from an external brake fluid leak.
If no pressure builds up when pumping maybe wheel cylinder or caliper.
Do not let the reservoir go empty.
System was not opened.
Pedal takes substantial travel to stop the truck.