Hissing from brake pedal?

 

Welcome to the forum

What Year Ranger?


Could be Atmosphere valve is leaking and/or Booster
Power assist brakes work by using outside air pressure
The engine's vacuum lowers the air pressure in the front half of the Power Booster
When you press on the brake pedal it opens the Atmosphere valve in the cab side of the Booster, allowing outside air pressure in to the other half of Booster which assists driver in pressing down on the pedal
If its leaking then you hear air noise in the cab

Unhook the vacuum hose from Booster and plug the hose so engine doesn't have a vacuum leak
Start engine and see if hissing is gone

OR

Depending on the year there is a Pressure relief valve in the cab for Cruise Control
Cruise control uses vacuum to hold throttle open when in use, the relief valve was a fail safe, pressing on brake pedal should cut cruise control if brake lights are working.............
But as a fail safe the relief valve dumps vacuum in cruise module disabling Cruise in that way

Unplug cruise control's vacuum hose to engine, plug the hose
See if hissing is gone

 

hey RonD
My ranger is 1999 w 3.0 L vsix.

 

Still used vacuum cut off for cruise, if you have cruise control