I have a 98 F250 4x4 that I did a few repairs to a couple of weeks ago before I took it to Mojave. I replaced the vacuum motor, switch, and the transmission was just rebuilt. Earlier I replaced disintegrated vacuum lines to the hubs. haven't checked the actual hub connections yet.

The 4x4 engages and I have dash air as long as there is no load on the engine. I know that there is a leak somewhere so I intended to start with the vacuum hoses behind the battery using my vacuum gage to test the lines.

The two reservoirs are attached to the battery box (which I didn't know). When I removed the box I must have broken the single line attached to the upper reservoir. So I have this 90 degree connector with 5 inches of tubing and I cannot figure out where it is disconnected from, and I don't know what it is for.

The lower reservoir has a connector with three tubes that go to the main vacuum and two lines that go to the two doodads that actuate the vacuum motor.

I hooked the batty back up and I still have dash air. I didn't try to engage the 4x4, which I think will also work.

I'm going to go out and take a picture of the mess hoping someone out there can tell me what I can't see. I will upload it on my next post.

Thanks for looking and I appreciate your comments.

 

Never mind the photo. I am not allowed.

 

from the looks of my vacuum diagram on my 98 250 5.4L 4X4 it should be "t'd" into the line from the lower going to the main
found a pic
http://repairguide.autozone.com/znet...52801e54d6.gif

 

You're right and I appreciate your response.

The schematic you provided is about the same as the one on my truck but yours is more detailed and easier to understand. My engine is a 4.6L and I don't know how much difference that makes. I've been staring at my schematic all day expecting to have an epiphany. I don't see a broken T that the line should have come from. All lines are accounted for. Unless something was done some time in the past.

I expect that you have the same set-up for reservoirs with an upper one with one line and a lower reservoir with three lines.

It's the upper reservoir line that I can't figure out what to T into. Would it be the large vacuum line going into the fender that looks like it goes into my cab down by the passenger side near the glove box?

This I'm not sure of because there is another line that goes directly through the firewall, I expect, behind the glove box. This line has a one way valve on it that is attached to what looks like 6 inch long plastic reservoir (?).

It looks to me like I have to T into one of these lines, I'm just not sure which one it is.

Thanks again for your help. Wish I could send a picture.

 

mmm its 11:17 pm here and my overhead light in the barn just blew when i went to look I'll try to remember to look tomorrow morning when i get back to my manifold stud from hell sorry couldn't look sooner

 

"Manifold stud from hell" doesn't sound good. I appreciate the effort. Good luck with Mr. aberrant stud. Relax and enjoy your Easter Sunday!

 

ok here's what mine looks
hope that helps
Happy Easter

 

Good work on the diagram! I appreciate your trouble. I can relate to what you are saying. I should have a broken T connector going into the fender it looks like. I have to go buy a T connector and do some more examining.
The upper reservoir is supposed to be for the engine and the lower for the HVAC according to other posts I have read.
What's funny for me after a year of trouble is the realization that I have never located my vacuum pump even though I know where it's supposed to be.