Why is air leaking out of this valve?
I have a Freightliner Columbia and anytime you press the brake pedal air leaks from the parking/service valve (Red and Yellow Knob Valve). I have looked at every lines, brake chamber and other places outside the truck because I thought it may have been leaking and the sound was just air rushing through the valve. No leaks outside anyplace. It does not matter if you press both knobs in, leave both out or any other orientation of the knobs. The outcome is the same. What can cause this and how do I tell which component is the culprit?
Is this a good question?