Just a quick backstory.

I have a 2005 Excursion 4WD with a 6.0. I have the typical vent to defrost problem when switching to 4WD. I have read every thread and sticky on diagnosing this problem and have found something I have not seen before. Vacuum at the pump is 15in/Hg. The reservoir peaks at 13 and slowly drops(~1in/Hg per minute). So, I know I have a slow leak somewhere between the pump and the PVH solenoid. Now for the unusual part. My vacuum on the drivers side when checked at the 90 degree elbow holds 10-11 in/Hg. When I test the passenger side(after capping off the drivers side, not reconnecting to the hub) I get maybe 2 in/Hg that drops to zero within about 20-30 seconds. I know these two lines come together at the frame rail and I have removed these from the connection and reinstalled. I do not see any visible breaks or kinks in the line. I can't figure out why one line will hold vacuum, and the other will not when they are both open to the same supply line. I checked to make sure the two into one connector was clear on both sides, blew air through it and then reinstalled.

My first thought is to replace all of the vacuum lines after the reservoir, but I can't even find part numbers for these lines. What have you guys used to replace these lines? Is there a generic vacuum line size I can pick up from a local parts house?

Thanks for the help, guys!

JG

 

If you have not already done this, hook up a vacuum tester (mity-mite or equivalent) to each hub individually. Bring vacuum up to about 12 inches and see if it holds.

My guess is that you have a vacuum leak on the passenger's side hub.