Where does this vacuum line go?

mike.marcacci

Adventurer
Hey everybody! I've got a bit of a head scratcher. In a nut shell, where is vacuum line #3a supposed to go? It was disconnected and uncapped:

vacuum pump.jpg

The van:
2003 Ford E350; Type-II Ambulance; 7.3L PowerStroke

The story:
An old, small vacuum line broke recently, locking the vents on defrost. So I went and bought a little mityvac hand pump w/ a gauge and found the problem quickly. In the process I also realized that I was pulling a very inconsistent vacuum despite the beast of a vacuum pump (the gauge needle bounced all over). I pulled a bit on the lines coming from the tree and wouldn't you know it, line #3a was just sitting there uncapped. I had been suspecting a leak for a long, long time due to the feel of the brakes (the amount of assistance varies throughout a stop and stand, but never to the point of concern) but assumed it was small and never got around to it. When I put on a cap, the needle stays exactly where it's supposed to.

I have the full ford maintenance manuals, and they say absolutely nothing about this line. There are only two diagrams in both volumes that even show the tree, and neither describe the function of the lines.

The line #3b goes to the rear HVAC system installed by the ambulance up-fitter to change from "cold" to "hot" (which has never worked... now I know why; we never cared, though, as we almost always wanted cold). Given this, I thought perhaps #3a might be for a removed ambulance component, but that the line is drawn in the diagram, and I was able to find one video on YouTube of a non-ambulance van with the same setup, and that line also points down (although without the tee for ambulance stuff).

I can't find any other line or system that it might be for, so I'm totally stumped.

Does anyone know where this is supposed to go? If you have a late-model E350 with a 3.7, would you mind checking yours?

Thanks much in advance!!!
 

Forum statistics

Threads
185,531
Messages
2,875,589
Members
224,922
Latest member
Randy Towles
Top