Yes, I have the service manual that covers the whole truck.
Are you talking about the filter that is mounted on the firewall that furnishes clean air to the hydro?
I had disassembled it and cleaned it when I first started on the brakes. Maybe a dirt dauber nest in it now?
I will get the manual out. Is the atmosphere valve inside the hydro? I will have to look at the manual to see where the vent is.
Could it be in the vacuum check valve?
Last edited by Old GMC Gold; 10/12/2014 3:21 AM. Reason: addition
