Hi. I am havin a problem with my 2019 Freightliner Cascadia. Once I stop and pull the parking brakes, while the foot still on the brake pedal, there is air blowin from the service line on the trailer and the grey exhaust hose on the firewall . If I take my foot of the brakes and push again it stops and no more leak. I changed the tractor protection valve but it is doing the same. Another thing I noticed is that when I release the parking brakes ,yellow button in , the hissing keeps longer than should and after stops hissing. I have checked for any leak but nothing. Thanks in advance for your help.
