Lots of great info here. Some more questions (hope I didn't miss them in posts)...

My '06 F150's 4WD won't engage. Noticed it the first time on a morning with -5 on the thermometer so was hoping it was the cold but no luck up in the 30s either. I have the electronic shift and I've had no noises, problems, etc. with the 4WD until this.

When I move the switch to 4H I get the 4x4 light on the dash and I can hear the shift motor doing something. Can I assume from this that the shift motor is OK or am I jumping the gun? Can the actuators also be heard moving/switching or are they silent? If water is present in the vacuum lines will it damage them when it freezes?

I should say that switching to 4L does give me the low ratio but no 4WD. Dash light works for this too. Not sure if this matters here but there it is.

 

There could be frozen water in the IWE system, not allowing it to work properly. This is a easy test if you have a garage or are somewhere where there isnt snow. Jack up the front of the truck. With the truck completely turned off, spin each front wheel and see if the half shaft spins with it, it should with the truck off. Now start the truck. Do the same test. The half shafts should not spin with the wheels. If you half shafts spin when they should and dont when they shouldnt, then your IWEs/System is probably ok. At that point i would focus on the 4WD shift motor. You might be able to hear it but it might not be engaging enough to turn everything. Crawl under the truck and on the transfer case is a little electric motor that looks like a windshield wiper motor. tap it lightly a couple times with a hammer and try it again. The 4WD shift motor tend to seize up every now and then.

 

O.k. I finally got around to working on my moaning sound again. I changed the front right hub and IWE and no change. However I got my Vacuum system running correctly as I found out by trial and error where everything is supposed to be connected up. I have total HVAC control again and engaging 4WD is fine but I am still getting a moan whether I am in 4WD or not. I will update my drawing to reflect what I found out today. I was thinking it was the right front because every time I turn to right the sound would go away and it sounds as if it is coming from the right front but who knows.

Tomorrow I am also going to pick up a Vac gauge to do some testing.

 

Updated IWE diagram for 2005 Navigator Ultimate.

 

Found my problem. It was the rear hub. Completely shot and that is what was causing my roaring. I did however replace all vacuum lines and understand the IWE system in the process.

 

By rear hub, do you mean the rear axle bearing?

 

No I have a 2005 Navigator with IRS so it is a hub just like the front.

 

Oh, i got ya, i never even thought of that before.

 

I knew there would be another hub because of the IRS but could of swore the noise was coming from the front and then when I turned to the right it went away. Just assumed to much on this one. The rear hub was completely trashed though as it was so worn it would actually catch on rotation.

I am going to try and rebuild this one as a back up. Gotta be some way the bearing presses in.

 

Many thanks to the contributors of this thread. Especially xjcamaro, even through I am a mustang guy

Heres my story:
Immediately after I put a leveling kit on my newly purchased 04 SCREW, I got the notorious whirring sound from the front driver wheel, and another awful rattlle coming from under the truck. I wanted to tackle the whirring first. I originally thought the whirring was a alignment issue (wasnt), then I thought it was a bearing or CV issue, which luckily I never got time to dig into. Then I realized yesterday the whirring went away in 4x4. So this morning I did a quick search on the forums and this thread popped up.

After reading the opening post (great job explaining it) I had a pretty good suspicion of what I had done. When I got home I looked behind the steering knuckle, found the vacuum line at the wheel, and sure enough it was popped off. I plugged it back in and all noises are gone. It literally took me longer to turn the steering wheel (to get behind the wheel) than it did fix the problem.

Today is a good day. Thanks again.

 

Glad it helped!

 

I know this is down the road a bit but I am fighting this now with my 04 at about 78K Miles. Kind of amazing that Ford didnt make this system "Vacuum off Disengaged" "Vacuum on, engaged" because I very rarely use 4WD. I am thinking that may be part of the problem. Something sticking from lack of use. Ford really screwed up putting this solenoid under a potential waterfall, but if they did nothing about the plug issue, Im sure they wont touch this one. I am surprised at the flimsy nature of the connectors and the vacuum system in general considering the outcome if there is a leak. Too many connections. By the way, I just simply cleaned the contacts on my solenoid with an emery board, and cleaned with electronic cleaner today and it seems to have solved my problem. I ordered a new solenoid just in case.

One question: I would like to make sure my lines are not contaminated, and I have a vacuum pump which I can use to purge them. Does this make sense?

Thanks to all for the great info on this subject.

JimA

 

Yes it makes sense or i think what you might be able to do is disconnect the vacuum lines at the wheels and on the solenoid then use compresses air (very gently) and blow the lines out, blowing into the open line end at the wheel. I made the mistake when i first started with this stuff of using compressed air to blow out my lines from the start of the vacuum line at the intake and blowing down. Well i blew out every check valve and blew up the reserve box. Sounded like a gun shot when it went off! lol

 

Thanks for your quick response. I bet you werent LOLing when you heard the bang. Do you know if the check valves are affected by water? I have a buch of check valves that are used with my HVLP spray gun that look very similar, Maybe I can use them, but I suppose I can just check the ones I have by blowing on both ends. I know there is one near the Solenoid, Where are the others?

This is truly a lousy design. I would have preferred a manual system to this engineering abortion. It aint like you cant forsee when you are going to need 4x4.

 

In my system there was a check valve in the feed line about 10" from the intake, then another one real close to the solenoid, those were the only ones i have. And yes, i was not LOLing when that box popped, cause at that time i had no idea that box even existed, then i tried to fix it with expoxy plastic weld, that didnt work, so i dropped $40 for a new one from the stealership. I just blow through mine to check them, or if you have a vacuum guage you can just apply vacuum to each side and you should have one side that hold vacuum, but even if the vacuum is leaking through the check valve a little, i would replace it.