I have been working on a 2008 volvo vnl plow truck. Regardless if the park valve button is in or out if I make a brake application air will constantly leak out the yellow exhaust line under the cab that I believe runs to the park valve. The unit does have both Yello and red buttons but does not tow and the outlet ports of the tractor protection valve are plugged. I suspect something in the system is back feeding just do not know what. The park valve (dash valve) has been replaced and problem still exists.
Exhaust line leaks air on brake application.
Discussion in 'Volvo Forum' started by bowtieboy77, Nov 15, 2021.