Chosen Solution
Hissing noise by brake pedal when applied, but little braking. Brake pressure good with motor off
If you here a hissing sound it can be one of two things . First check the brake fluid reservoir. If the fluid level is down the his is probably the piston in the master cylinder has blown a seal . If the fluid level is fine then the hiss is probably from the power assist cylinder . Changing out the vacuum assist is easier than the master cylinder let us know what make and model your car is and year and we can provide instructional video for each job
Check your bearings. You may need to replace them.
