Well..like I said, went to the dealer before and they replaced my solenoid with the new style covered one. I went out to do the checks you so beautifully described. The first thing I noticed on the solenoid was the two van lines, and low and behold, the plug for the solenoid..UNPLUGGED! I guess there's no guarantee the dealer can do no better job than I could've. I could've left that unplugged for free! Seriously, it works fine now, and thanks for your information. I probably never would've known how to troubleshoot for that otherwise. I'm sending everyone I know with a F150 your post.

 

LOL, wow! Happy you got it fixed! I once went and had some work done at the dealer because I just didn't have time before a 800 mile trip. It was the middle of winter and bone-chilling cold out- near 0 the entire way. Part of the work I had them do was flush the radiator. 400 miles later I checked the oil while filling up and noticed that the radiator reservoir pressure cap was on crooked. Most of the coolant had leaked out under pressure. This was on a 2000 Windstar. I have no idea how I didn't smell coolant, or how it didn't overheat on the interstate. I was PISSED! Moral of the story- always inspect your mechanic's work!

BTW, if your solenoid was unplugged, that means that the front end was locked in all the time. That would have cost you a few MPGs most likely, but otherwise it won't hurt anything.

 

My new "best" reference for 4x4 issues. Excellent.

 

For some reason I can't edit my posts in this thread anymore... maybe there's a time limit?

Anyway, here are some pictures. This is the vacuum line, starting at the brake booster. The red arrow here points to the first check valve in the vacuum line:


From there the vacuum line is clipped to the back top of the intake plenum behind the throttle body and then loops up again. The red arrows point to each loop of the vacuum line. You can see the check valve in the driver side loop that we looked at in the first picture:


Here is another check valve in the line... getting closer to the IWE solenoid now:


And here is the IWE solenoid. But what's this? Another check valve? Yep, the tiny red arrow points to it. The T-fitting in the vacuum line that goes to the vacuum reservoir is right next to that check valve but not visible in this photograph. If you look on your truck and move some of the vacuum lines aside, you will see it.


The big yellow arrow above points to the hood on the new style solenoid. If you have the old style, you won't have this hood. Notice the water stains on it already. That's a new valve that I put in a month ago and hasn't seen but a couple rain and snow storms. Water definitely gets up there, which the hood is designed to protect from.

The blue arrow points to my old solenoid, which is not connected to anything. The old metal bracket and the new solenoid hood both include a spot for another solenoid. I just took the old one and moved it over so I would have a spare there if I ever needed it.

The last part of the vacuum system I have a picture of is the vacuum reservoir behind the battery:


A vacuum line (control side) also comes off the solenoid and goes down to a T-fitting, and that then leads to the IWE at each wheel.

Hope that helps.

 

I"m having a problem with mine. It's done it to me twice now. The grinding sound, then a bump and it goes a way. It lasted 20 seconds or so the first time. It took me that long to change lanes and pull off the road. It did it to me again the other day for about 5 seconds. The noise is coming from the left side. I saw this thread last night and jacked up the truck today to check it out. Both left and right side IWE's are engaged while truck is off. Both of them stay engaged while truck is running and in 2WD mode. They aren't locked in with the TC though. When you switch it to 4WD, they lock in with the rear and won't turn. I checked for obvious problems with the lines to each side and under the hood and don't see anything. I haven't pressure tested everything yet, I was just looking for melted spots or places where they might have wore thin. I'm leaning towards the solenoid being bad, but I'm probably just going to take it to the shop and let them trouble shoot it.

 

Your next step is to.get a vacuum gauge on the lines @ each IWE, one at a time, to see if there is vacuum there in 2WD, engine running. Sounds like your IWEs are always engaged, which costs you fuel mileage.

 

I recently replaced both IWEs and the solenoid. I thought my problem was solved but I am now feeling the grinding again. Engine off 2wd, hub and half shaft spin freely with no restriction like you talked about. Engine on 2wd, hub and half shaft spin just as freely as when engine is off. Engine on 4wd hub and half shaft are locked together and will not spin. I went through the TCM diagnosis and that seems fine. I am assuming I should start by vacuum testing the system. Does anything else stand out regarding my symptoms?

 

Yep, you need to vacuum test. Test all the check valves.

 

Ok thanks. I need to get a vacuum gauge and get to work. Ill post my results when I get to it.

 

Thanks for all the pics and explanations! You're a tremendous help!