Originally Posted by bob h (Post 436778)

Even if the red dash valve leaks out to the TP control port, there is still no air on the blue line unless a service brake application is made.

So, in order for air to leak out the blue line, you would require a 'second' leak; the first leak is through the red dash valve, the second leak through the foot valve (where the blue air comes from), and it's VERY unlikely that foot valve air would leak from 'supply' to 'delivery'.