Everything You Wanted To Know About The IWE System....And Then Some!
 

After my recent experiences with the complete IWE system i decided to write up a description of the system and troubleshooting. Hope this helps out some people!

Maybe this can become a sticky!

When the system is working correctly, vacuum is placed on the system unlocking the hubs while the truck is running. When shifting to 4WD vacuum is relaesed, locking in the hubs. A vacuum leak at any part of the system can cause failure.

When the engine is started and running, vacuum is exerted on the entire system, unlocking the IWE actuators. When the engine is turned off or 4WD is engaged (either by floor shifter of dial selector) vacuum is released by the IWE solenoid to the actuators at the wheels. So vacuum to the actuators at the wheel unlocks the hubs for 2WD and release of vacuum by the solenoid locks them for 4WD.

When the vacuum builds when the engine is started, the vacuum from the intake via a vacuum line exerts vacuum on the entire IWE system all the way to the actuators. The first check valve locks the vacuum at the highest vacuum that is exerted from the engine from that check valve down. The vacuum box now holds that highest vacuum exerted also. The second check valve located right before the IWE solenoid holds the highest vacuum to the actuators from what has been exerted from the engine.

As you start to understand the vacuum system and series of check valves, you will see that the vacuum box that is located between the two check valves does in fact act as a reserve. When you engage the 4WD, vacuum is released by the solenoid and locks the line from the solenoid back up, the release happens from the solenoid and to the actuators. This process allows the lines and vacuum box between the two check valves to hold the current highest vacuum even though the engine vacuum is constantly changing and the vacuum from the second check valve to the actuators have been lost. When 4WD is disengaged, the solenoid is opened back up, the high vacuum from the reserve from the vacuum box is then used to then exert vacuum on the lines to the actuators unlocking the actuators no matter what the vacuum from the engine is. When this little bit of vacuum is lost in the reserve it is then rebuilt from the engine when vacuum is increased from the intake.

After saying all of that and you think about what the manual says about turning the 4WD on and off, you notice that you are supposed to activate and deactivate the 4WD while under a certain speed and while not accelerating. This ensures two things, high speed engageing and disengaging of the gears in the hubs which can cause mechanical damage does not happen. It also allows a quick window of no load and low RPMs from the engine, hence high vacuum from the engine, that will quickly replenish the high vacuum to the entire system and "locks" that vacuum between the two check valves and reserve box for the reserve, as well as from the second check valve to the actuators.

This, when working correctly without any leaks always ensures a high enough vacuum to keep the acutuators unlocked when your in 2WD, or unlocking quickly when shifting from 4WD to 2WD. A leak in one of the lines,the reserve box, or an actuator, or a faulty check valve will allow a leak down in vacumm somewhere in the system that will allow the actuators to possible try to engage or close to it when not needed while driving, giving you the grinding or whinning noise of the gears of the actuators trying to mesh together at highway speeds.

To test the vaccum system, get a good vacuum pump with a guage on it, about $60 (or cheaper) at alot of parts stores.

-If when you try to shift into 4WD and it will not engage, most likely your solenoid is not working and releasing the vacuum to the actuators and engaging the hubs. Replace the solenoid. This might happen because of the early design of the IWE solenoid with lets water run off the cowl right down on top of the solenoid possible shorting it out. The new style solenoids have a rain cover on them to prevent this. This is all being said as long as you know your shift motor on the side of the tranfer case is working properly.

-If your in 4WD and it will not shift out, the solenoid is not opening back up to let vacuum release the actuators. Replace the solenoid. Again if the shift motor is working.

-If you hear a grinding or whining of gears at certain speeds or loads you probably have leak in your vacuum system somewhere and your vaccum is dropping to or below the 5 lbs of vacuum needed to keep the actuators unlocked. Check the following:

One wheel at a time unplug the double vacuum hoses from the actuators at the wheel located behind the steering knuckle. Put your vacuum pump on the big hose fitting and pump up the pump. If it is woking correctly you will be able to build up vacuum and it will hold. A vacuum loss of 1 lb over 1 minute is acceptable. If you can not build vacuum or is leaks down very fast, the seals on the actuator are shot and the actuator needs to be replaced.

Next check your lines from the solenoid to the actuators at the wheel. Pull the double vacuum line off the solenoid. Pull the double vacuum line off of both actuators at the wheels. Plug the hoses at the wheels. (you only need to plug the big hose a the wheel, and make sure you have a good plug that seals 100%) At the double hose that you took off the solenoid, trace the lines, you want the line that goes down to the wheels, not the one that goes to the intake. Take your pump and connect it to the line end from the solenoid that goes to the wheels. Pump the pump up and see if the vacuum on the guage holds. If it does not and leaks down, you have a leak in your lines between the solenoid and the actuators. Check the lines very thoroghly from the solenoid to the wheels, its hard to get to some of the lines, but they all need checked, look for cracks or breaks. Replace the lines with factory ones from ford or make your own, like i did with bulk vacuum hose and some fittings. If the vacuum you create with the pump holds your lines are good, but still look them over for obvious faults.

Then you will want to check the vacuum reserve box that is mounted behind the battery on the battery tray. You will have to remove the battery and battery tray to access it. Once removed and the vacuum line disconnected from it, connect your vacuum pump to the fitting on the box and pump up the pump, if it pumps up with vacuum and holds it is ok. I fit doesnt build vacuum from the pump or leaks down, the box is leaking and needs to be replaced (ford only part).

Now plug the line you removed from the vacuum box, this line runs to the intake with a "T" in it. The line from the "T" goes to the solenoid. Plug the end that goes to the solenoid also. Unplug the same line at the check valve that is close to the intake. Connect your pump to that end of the line and pump up the pump. If it pumps up vacuum and holds, that line is ok, if it wont pump up or leaks down then there is a leak in that line, replace, fix, or make a new line.

There are two small check valves in the line coming off the intake. One close to the intake and one in the same line close to the solenoid. Pull those check valves off and check them. An easy way to check them is to blow (with your mouth, not compressed air, this will blow them out, i know) You should be able to blow through one end and not the other at all. Or you can check it with the pump. One side of the valve will say "VAC" connect your pump to that end and pump it up. It should pump and hold without any leak down. If it does not then replace it. If it holds its good. If one or both of these fail, the high constant vacuum will not be held correctly in the system and while driving, the vacuum could drop too low and try to engage the actuators.

If all of this checks out ok check the vacuum straight from the engine. From the line coming off the engine connect your pump to the line and turn on the truck. Watch what poundage of vacuum shows up on your guage (you will not have to pump it up) should be anywhere from about 17 to 22. Ive read that 20-22 is normal but mine likes to hover around 18-19 at idle. If this reading is too low you might have another vacuum leak somewhere else on the engine.

Remember the 4WD engagement or lack there of is considering that you shift motor on the transfer case is working properly.

If you suspect that your system is malfuncting and you are not able to test it right away or want to drive and not damage anything, disconnect the line coming off the intake at the check valve and plug both ends of the line. This will not allow any vacuum to reach the system and leave your hubs locked in all the time. This is fine and wont cause any damage as long as the hubs lock correctly. The half shafts and front driveshaft with the front differential will turn but the 4WD will not be engaged. You might notice a drop in MPG, but it is now safe to drive.

I hope that my investigation into the system and explination helps alot of people understand the system and help troubleshoot it. Anybody feel free to add to this, but i think i covered it pretty deeply.

This is a rough layout of the IWE vacum line system. From what i can gather and understand from the vacuum system for IWEs, there are two check valves and when working correctly and without any leaks in the vacuum system they hold the vacuum to the IWEs at a constant vacuum even thoguh the vacuum will change at the intake with engine load and RPMs.

https://www.f150online.com/forums/me...um-drawing.jpg

nice write up, subscribing in case of future issues!

I beleive its correct, if not its really close and some others can correct me if needed.

I updated the diagram for the IWE vacuum system. Thanks to SSCULLY for redoing it for me and taking his time to do it. Hope it helps!

perfect
 

xj, you may have saved me some serious headache with this.. Thanks for the time and effort on putting this together.

No problem!

Great writeup! This post and several by TNF150 are great for identifying and fixing the most common problems with the 4x4 actuation system on late model F-150's. Thanks for taking the time and effort to document everything so nicely.

Good write up xj!
 

Looks like I suffer from the dreaded IWE vacuum leak now, and this will serve as good guideline for me. Started hearing that noise under a light load as I was driving last week, so I decided to pull the battery and take a look, and sure enough there's an open vacuum line staring me in the face. Going out there now to try and fix it, only problem is, I can't find the other end of the open vacuum line, I trace it coming from the front passenger wheel to where it is open and then I am lost. Thanks for the write-up xj.

you may be looking at a vent line. read the whole post ...

Yeah, I read the entire thread and just re-read it and I see where I missed it on the diagram. Looked for the vent line on the drivers side and haven't located it yet, but I'm sure I will. I did find a broken vac tube on the passenger side and fixed it. Will have to take it for a ride and see if the noise is still there.

subscribing

I wish mine had just been a vac line!

was it a black line and it had no connect to?

I replaced my brakes about a month ago, and my IWE's and my IWE solenoid. My drivers side IWE was destroyed, I have the 2004 lariat, so i have the uncovered stock solenoid, and opted to purchase the one with the cover.

I still have the low vacuum leak rattle, so I pulled the hoses off the other day and check one hub at the time, and I have no vacuum leak at the system, it's holds 23 PSI, so i'm thinking I should have replaced my hubs as well, my truck has 117,000 miles.

IS there a visual inspection I can do on the hubs before I order new ones? Or am I just gonna have to order them, and hope it's the problem....I recall looking at them closely, and they looked great....

izzy

I had a similar issue. I replaced my IWE solenoid and had my truck vacuum tested. It turned out that I didn't have any leaks in my system and my IWE solenoid was working properly.
I took my truck to a ford mechanic and he simply raised the truck up on a lift and removed the vacuum tubing by the hubs, spun the wheels a few times and a ton of rust blew out of the hubs. Since then my issue has been corrected.

:D Sometimes it's the simplest of remedies that work so well! :)

Chalk one up for the local Ford mechanic! :thumbsup:

I'm so gonna try that! You guys are AMAZING on this forum!

Izzy!

So the other day, I tried Maniac01's suggestion, of removing the IWE vac. lines, and spinning the wheels, I tried a couple of times. Sadly, it didn't resolve the low vacuum shutter that I hear in the IWE's, I checked the vacuum again, and there is no leak off, they hold well, so I took a piece of vaccum line and removed the lines from the engine to the solenoid, and hooked the top and bottom together, to bypass the solenoid. The rattle still occoured, but it didnt' seem as loud. It's worth mentioning, this vacuum line was rather long, it's from my vacuum pump kit, and i used the plastic fittings to make the lines fit snuggly. I'm kinda lost on this....lol! It could be the hubs, or could be that solenoid, it's a new solenoid, but we all have purchased poor parts in the past, what do you think?

izzy

Ok, first, let me say, I AM AN IDIOT! I hadn't read the ALL the information that was availiable on this thread, so for that, I smack myself :thumbsup:

But, I digress. So, yesterday, I printed it out, went home after work, and checked all the lines, there were no leaks. The vacuum box, didnt' leak. BUT, the check valves, both, after 118,000 miles, had failed. SO, I called Ford, and shocker, the parts guy said he had no idea what I was talking about, so I drove to an autparts store, and walked into the HELP section. There, on the shelf, amid a bright light, were two check valves. After two check valves and 10 dollars in parts to make them fit, my IWE system has stopped making the low vacuum noise, and for that, I thank you.... :beers:

nice explanation, subscribing!

Excellent Izzy! Likely saved enough for a dinner out!

My issue started out making noise only when real cold it went away though. Now when I lock my truck in 4x4 and put a load on it there is a grinding sound coming from the passenger side, which doesn't spin at all, and the driver side makes no noise what so ever but also doesn't spin... Can someone help me narrow down exactly what can cause this?

Much like a rear axle with open differential and one wheel on ice or jacked up ...
... if one IWE fails to engage fully and instead the splines slide across each other making that racket, there will be no power transmitted to either front wheel even though the other IWE engaghes ...
... unless you have a locker differential in front which I doubt.

Sounds like you have a IWE that's not engaging for some reason.

So I'm having a grinding noise coming from the right front for about a month now. It sounds like fine splines grinding to me but anyway... I can be driving along and it will just start this wild grinding sound all of a sudden. The thing is, I can engage 4wd and it completely goes away. Disengage and sometimes the noise comes back, sometimes it waits a bit. Is this the same kind of thing you guys are talking about? I'm totally at a loss on this one and my dad which has been a mechanic for 40+ is out to lunch on it too. I'm hoping it's nothing major but if it is I need to get it taken care of ASAP before it causes other problems. What's bad is with the "quiet steel" that these trucks were built with, if I can hear the noise as good as I can in the cab I can only imagine what it sounds like outside. Makes me cringe... Btw, '04 SCrew, 5.4, 145k.

So would it be just that seal? If its just one what would cause just one ? Help me narrow it down.

The rerason this is happening is that the whole IWE system depends on vacuum. At rest (no vacuum), your IWE's are actually locked. Start the truck up - or put it in 4WD - and the system applies vacuum to the IEW's and disengages them.

Now to your point. You either have (or had) a vacuum leak someplace or an IWE go bad in the past. What's happening now is that it's partially disengaged and thus the grinding noise. It may be a bad Solenoid, Vacuum Line or Check Valve that caused it and you need to track it down. But, since your IWE has been partially disengaged for so long, it's probably bad too.

Hope that helps.

Its just one side.

When this first started happening one side of the truck would whine when it got really cold out. It didn't happen all the time only after the truck sit in the cold weather. It would make a whining/ grinding noise. It would go away. Now my truck when I put it in 4x4 and put strain on it, it just grinds and my front wheels do nothing.

If it were a vacuum check valve wouldn't it cause both sides to mess up? It has to be right around that side correct?

Not at all unusual to have just one side go. That's what happened to my 2005. And remember, once you zing an IWE for long enough due to a vacuum (or should I say lack of vacuum) problem, it's toast and needs to be replaced. That grinding you hear is an IWE getting ground up.

Subscribing

That helps my knowledge and diagnosis a ton but help my wallet absolutely none!!! Seriously though, thank you for your insight on the issue. I just got a wild hair and decided to get on here and take a look and bam, there it was, similar symptoms and all. Once again, great site and great members here. Thanks for the help.

Glad we were able to help. Remember though, if you're half way handy, you can replace virtually anything on this system right in your own garage. That'll save you a ton of coin.

I'll start by saying I'm not very mechanically inclined in the first place but when I started researching the issues I was having (it would sporadically try to engage while driving for no reason) and ran across this thread I decided I could give this a try. I am without question having vacuum leak issues. The IWE's are both engaged while the truck is running. They appear to be working fine when I hook the vacuum pump up. They both release at exactly 5. They also will hold 20 for a couple of minutes without a problem. I am having trouble when it comes to checking the lines down to the wheels. Can someone tell me (or pics would be great) exactly where I need to hook up the pump to vacuum the lines down to the wheels. I unhooked the lines from the solenoid and pulled them out to where I could get to them. I went below the air check to a T. The drivers side of the T goes back to the other air check and appears to the manifold. I hooked the passenger side of the T and hooked the pump up with the lines off the wheels and plugged once and connected to the wheels once. They both hold pressure just fine. The problem that I have is when it is connected to the wheels this did not disengage the IWE. I either have the wrong line and am vacuuming the Vacuum box or the line is clogged. I think I may just have the wrong line though. I did not take the battery and box out as I did not have time at this point. If I dont get it fixed by saturday that is the next step.
Thanks for the helpful information so far as I am sure it has already saved me a fortune from not having to take it to the dealer for something that so far seems fairly simple.

XJ, great write up and guidance along the way for everyone with IWE issues. Hopefully you can help me with mine. For a few months now I've been getting the 4wd to engage only part of the time. Sometimes it never skips a beat and sometimes it doesn't beat at all. I don't hear any grinding noise or any of that. I did replace the IWE solenoid and it worked immediately after that (although it could have just been one of the times it decided to work.) Recently it hasn't worked at all. My guess is that the transfer case motor is bad and should be replaced. What are your thoughts? I haven't tested the vacuum lines, but it seems like the vacuum lines are only an issue if you're hearing grinding noises. Is that true? Any advice you (or anyone else can give me) would be greatly appreciated. Thanks.

The first question I'm going to ask is about when it doesn't go into 4x4. Does the indicator on your dash say it's in? If so, you have an IWE / vacuum problem because the transfer case is shifting. If the indicator doesn't show it's in, then you have an ESOF motor problem. If it looks like an ESOF problem, you might want to put the truck up on a lift and have somebody move the selector switch back and forth while listening for the motor moving the shift fork. If it doesn't move - and has power to it - the motor is quite easy to replace.

Thanks for the quick response. No, it doesn't go into 4x4 when I select either 4-hi or 4-lo. I will get a buddy to work the switch for me this weekend and try and listen for the motor. How would I go about checking that the motor has power to it?

The short answer is "test light." I don't have a wiring diagram handy, but if you ground the test light, you should have power to at least one of the wires in the modular plug. If the motor doesn't start when your friend moves the selector switch, try lightly tapping the side of the ESOF motor. This will sometimes wake one up. If it does though, the motor is probably on the way out the door.

great wright up helps alott.

No vacuum on my 4x4
 

Ok I'm having issue of no vacuum coming into the reservoir or the solenoid. Can someone please help
it's on a 2004 f150 lariat 5.4.