ODD sound from brake booster (1 Viewer)

[Camper Dave]

Recently changed front brake hoses. Bled the lines before and after driving. Started making the oddest sound when applying brakes. Pedal is hard, put does go in after starting motor. Makes this sound when vehicle is off/running. It seems to be coming from the input shaft of the brake booster. No leaks. Check valve is working. I have changed a few brake boosters but always due to hissing sound or just complete failure.

Anybody hear this before?

 

[JohnnyC]

Are the pivot points lubed? Imho it sounds like dry dust/rust friction

Odd sound .... I agree

 

[Camper Dave]

They sure are, I unbolted master cylinder and the sound went away. However, I did not have an extra hand to apply resistance why I pressed the peddle. When I have replace a master cylinder in the past, failure always resulted in a mushy brake peddle?????