Thank you for the feedback gentlemen. But - this is still not making sense to me. At first I though Yeah - a hole in the booster diaphragm but then I traced everything. Truck sat for ten years in a field before I got it but the original owner told me the booster was replaced shortly before he quit driving it. One of the reasons they replaced it was that they could not get it to run right. I know that doesn't mean it doesn't have a diaphragm leak but suggests they tried to correct this problem previously.
Just to detail things here a bit. (See Images) My finger points to the line that begins at the bottom of the brass check valve. This line pulls constant vacuum and there is no way it would not because it Tee's forward of the brass check and goes directly to the motor with the other part of the T going to the booster. From the brass check it drops down the firewall and enters a VALVE of some sort mounted on the frame. From there it exits that same VALVE as a different line (on the same side it enters only higher) then curves back around and goes back up to the cab filter. With this routing it IS going to pull constant vacuum unless there is something in that VALVE that is suppose to stop that.
Now I assumed that the VALVE in question was only to change which side of the rear differential two speed box it would send vacuum to. In other words activating either HIGH or LOW speed. But if this valve also somehow is suppose to cut off the FILTER VACUUM then it is not doing its job.
Can anyone confirm my hypothesis?
By the way just threw in that image of the truck. Was painting the bed yesterday.
Last edited by IDidIt; 04/08/20232:25 PM. Reason: detail change
