The Cummins dealer in Columbia pulled my sticking PAC Brake and discussed the conditions found (occasional sticking closed) with PAC Brake. The entire brake asswembly must be replaced. Strangely a new PACBrake with all fittings is cheaper by $60 than the valve body only. PAC Brake was helpful to me by phone and e-mail and asked that Cummins call them for trouble shooting sugggestions.