2001 Toyota Tundra SR5 Break help please

The breaks go down slowly but will pump up sometimes they go to the floor just idling but when you pump them they are good. They have been bled but just can't get the last little bit of air out. What could be causing this? Thanks

 

If you are sitting at a light and holding your foot on the brake, it randomly goes to the floor? I'm wondering if the vacuum booster is starting to go out due to a vacuum leak.

 

Has anything been replaced recently? Sounds like air in the system. Some components are a bi*ch to bleed.

 

I had the same issue with a Brand X truck many years ago ~ the master cylinder was leaking internally.

 

either a master, or its not fully bled, has the rear portioning valve been bled? to properly bleed these trucks you need to pop the bleeder on the LSPV on the frame that the rod on the axle attaches to. then bleed the wheel cylinders

 

Make sure the rear brakes are adjusted before bleeding.

Although it sounds like possible failing master cylinder or vacuum booster.