I believe I'm having intermittent IWE issues. Truck seems to make a humming noise when its cold and then kinda goes away when it warms up. I unhooked the line coming out of the solenoid and it went away. Originally I thought I had a brake issue because it only happened when I was on the brakes. Then it got a little bit worse and then I thought it might be a wheel bearing going bad. Then after researching it, it sounds like this has the same sound and feel as a wheel bearing going bad. I described it like a bad wheel bearing or having a mud tire sound coming from the right front. I found that the check valve before the solenoid seemed to have a leak so I replaced that and the issue is still there. Then I plugged the line going out of the solenoid and into the IWE's and the issue seemed to go away (I think. Its hard to say because once the truck warms up it won't make much noise if any at all). I was wondering if anyone had a good diagram of the vacuum system. I plan on doing vacuum tests before going too crazy and replacing the IWE in the passenger front. Its driving me nuts because I just bought this truck a few months ago and want to catch the issue before it gets too bad. I'm pretty sure its probably the passenger IWE but I'm hoping its just a leaky vacuum line or something. A Mechanic I work with that used to work for Ford thinks its the solenoid, but he hasn't looked at it, I just described the issue to him.. But from what I can tell, that seems to be working, it has vacuum when in 2 wheel drive and no vacuum when you change it to 4 wheel drive. I just know there has to be a way to diagnose it before just throwing money and parts at it. Any help would be appreciated! I'm following this past post but its not for an Ecoboost so I figured I'd see if anyone had a diagram https://www.f150forum.com/f38/iwe-testing-validation-409087/

 

There is a good video of a guy going through all the checks on Youtube. He is working on a brown 2012 I think. Not sure of an eco boost, but my 5.0 is just a line off the brake booster to the check valve. The 3rd line on the check valve goes to the reservoir tank, then one to the solenoid, then off the solenoid to a T, then left and right side. There are pictures on some of the ford parts lookup sites. I replaced my check valve, but no change. Mine only grinds when I lose vacuum during aceleration. Did the thumb test with the truck running. Truck in 4x4, no vacuum on the service side of the solenoid, 2 wheel drive, vacuum on the service side. Pull the line off either hub, vacuum out there too. Jack up front end. Truck shut off, spin wheel, axle should spin. Start truck, spin wheel axle should be free. I think my tank might be leaking, or my new check valve might be faulty. Going to have to buy a hand pump I guess. Chances are if your noise is only one side, you need a new actuator. If the problem was the solenoid, it would be both wheels

 

EcoBoost is an engine option ...

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Another test if you suspect the solenoid, is to bypass it by pulling the line off the service side, and fasten the line directly onto the one way valve. I did that with mine, even though I'm sure that's not the issue. Still tried to lock in while under aceleration. If you are having issues with one side, I'm willing to bet it is that actuator.