Hey guys,

I know there have been some really great threads on the IWE's (read through all of them, and think I'm close to my answer), but I cant find anyone else thats experiencing quite what I have..

My 2007 F150 4x4 XLT SCREW will shift in/out of 4H/4L just fine, not a problem there. Also, its not trying to lose vacuum while driving and engage the hubs (no grinding, etc).

My issue is that when the truck is running, and vacuum is applied, it keeps the actuators disengaged and in 2WD as they should. What I notice is that when the engine is shut off, it appears to lose vacuum at the IWE's and they engage. How this is being noticed is that once I go to re-start the truck and reverse out of a parking stall, I get a very loud "POP" from the driver's side, then it goes away, and the half-shaft stops spinning.

The question I have is - when the truck is off, should that whole IWE system, from the solenoid, through the vacuum lines and down to the IWE's at the hub hold vacuum? I have put a vacuum gauge on the IWE's themselves and think they are leaking, as they wont hold vacuum, which could be my entire problem in the first place. Just curious if that system is designed to stay air-tight when the engine is off, or if leaking down is normal, then when the engine is restarted it will disengage the actuators at the hubs, providing pop-free 2WD mode.

Sorry for the ramble, just trying to get a couple questions answered prior to taking the plunge to replace the IWE's. Thanks guys!

 

No they should not be air tight when shut-off. They will lock back up when engine off.

 

OK, that makes sense. It would appear to me then, when I re-start the truck that the driver's side just isnt pulling it back strong enough, probably a good candidate for IWE replacement.

 

I would check the vacuum lines to make sure they are not partially blocked or cracked before I would cough up for a new IWE.

 

Yeah, went through that exercise yesterday. When I put my vacuum pump/gauge on the IWE it wont hold vacuum. So, unfortunately had to make a visit to rockauto to get some new parts on the way.

 

YES, your system will hold a vaccuum !!!

use a 3 way "T" and place the vaccuum gauge at the IWE soleniod inlet after the check valves, run the engine - when you shut off engine the check valves should hold vaccuum if not you have a leak somewhere. i have found 3 leaks in the ridged plastic tubing ford used on these, the worst was the vaccuum canister behind the battery, the rigid hose goes directly into the canister fitting and was melted away. all the leaks found in the rigid plastic appears that the plastic was melted by chemicals.

I wish it was easier to post video or pics on here, i could show pics of vaccuum being held while engine is off - i say this because i know members on here will say other wise.

side note - when removing battery to get to the vaccuum cannister i found battery had a crack and was leaking acid, i believe that is what damaged canister line, the others i believe were cause by previous owner as i found all this days after buying my 05 lariat. ya i bought it cheap - dealer took a few grand off because i said i would fix everything wrong with it.

 

FF, if the OP hooked the pump/gauge directly to the IWE and it didn't hold, that's a bad IWE, don't you think?

 

Hey guys - thanks for the advice. I went ahead and replaced the IWE on the Driver's side (the old one wouldnt hold vacuum with a pump/gauge, and was shot. Also replaced the solenoid behind the battery).

The problem still remains, though I've been able to learn a bit more about it. My truck still will not fully disengage the front axle's in 2WD mode. Thats where my popping noise is coming from, sounds like a CV joint binding up while in reverse. It wont make the noise while moving forward, so, I guess I may have to spring for a new CV joint or axle down the line.

With a brand new IWE, good vacuum (will hold 20in/Hg at the IWE) it still wont pull it out enough to fully disengage it.

Any other ideas?

 

Just another update after some additional troubleshooting. I replaced the solenoid behind the battery with a Dorman product from RockAuto, and I think it may still be junk. I had it up on 4 jackstands messing with it, making sure that the T-case wasnt spinning in 2WD, and all that checked out.

I started to unplug vacuum lines at various spots in the chain to test for leaks, and I found that once I took it all apart and put it back together, I had vacuum on the "out" side of the solenoid while the truck was running again.

Seems to me that I have good vacuum coming off the intake, the check valves work, and the solenoid (in 2WD) was not functioning properly to give vacuum back to the system to allow my front end to not spin while in 2WD.

For the meanwhile I can bypass it and put vacuum to the front IWE's directly from the intake, rendering it a 2WD truck while I wait for my local ford dealer to get the FoMoCo solenoid in to replace behind the battery.

Been a fun experience learning and troubleshooting this one... thanks again guys!