OK, here's mine: myself and a mechanic friend went through my system today. He tested the passenger actuator and it seems to work fine. Tested the drivers side and it is seized, so I need to replace the vacuum hub assembly. When driving, there is a whining that kicks in after a while. It's not there all the time so it can only be the 'working' passenger side engaging intermittently. He tested the vacuum lines for leaks. We came to the two lines coming from behind the engine and the one going to the 4x4 system appeared to have a very weak vacuum. The line going to the solenoid on the fuel rail(don't know what this is) was much stronger in vacuum. We switched the lines for now to keep the passenger side from locking in(hopefully). Any insight into this is appreciated and I'd like to know what the vacuum line going to the solenoid on the fuel rail is.

Thanks

 

Could there be leak at the connection point for the weak line? Anyone?

 

The line going to the actuator on the fuel rail i think is the fuel pressure regulator. I dont think the vacuum lines for the fuel and IWE are on the same lines. What i would do to isolate a leaking line is to start disconnecting some vacuum lines and plugging one end while connecting the vacuum guage to the other end and see if all the individual lines are holding vacuum. What could be happening is that there is a leak in the seizing actuator and letting vacuum out and letting the other side try to engage. Its going to take some testing to see just where your leak is coming from. Remember to check the check valves as well. But since you know one IWE is bad, i would start there.

Also what you are calling a seized IWE could be an IWE that has a leak big enough in it that when you try to apply vacuum with a tester(guage) that the leak wont allow any build up of vacuum and never allowing that wheel to disengage. Which inturn the leak is also letting the other side partially engage while the engine is working harder and dropping in vacuum. Try some of that and see what happens.

 

We tested all of that only to find the line coming from behind the engine was a weak vacuum. We worked our way back to that and discovered the other vacuum line coming from behind there and going to the fuel rail. There were no leaks in the lines or at the connections. The check valves all seem good. I'll replace the actuator and see what happens from there. Since we switched the 4x4 system to the stronger vacuum all should be good then I hope. Then I have to figure out the damn intermittent stiff steering issue I have!

Thanks for the reply

 

Im not sure i know what your talking about when you say the vacuum line coming from behind the engine. On my setup i have one vacuum line that off the side of the intake and goes behind the battery to the solenoid. Then from there a line comes off and goes down toward the passenger wheel and splits, one end goes to the passenger wheel and the other goes along the cross member to the driver wheel. Maybe they changed the hose routing after early 04 like mine. But i would be careful what vacuum lines you start unplugging and plugging into. The one going to the solenoid on the fuel rail controls your fuel pressure. So if your tapping into that and starving your fuel pressure regulator for vacuum you might run your truck lean or rich depending on the situation. Just a thought.

 

If there was a problem with the fuel pressure would I not get a code?
The vacuum line for the 4x4 system and the line for the fuel rail both originate behind the engine somewhere. I can't see where.

 

Your setup must be different than mine, my 4x4 vacuum line originates on the passenger side the the intake manifold and has nothing to do with the fuel pressure, and yes you would probably get a code.

 

Thanks again for a great, informative thread! Before now I had no idea how the newer 4x4 systems worked. Now, thanks to this thread and my dilemma, I'm pretty well versed in them. Mine had a bit of a twist I thought I might add...I may not be 100% accurate in my diagnosis, but it sounds good to me and it works now.

I have an '05 F150 Screw that I bought about 2 months ago and it started the grinding intermittently about a week ago. It did it 3 times that I know of (if the radio was turned up I couldn't hear it). Followed this threads schematic on troubleshooting the system and could only find a weak check valve, which I replaced. While going back over checking for more leaks, problems, etc. I lost vacuum at the actuators while in 2WD so I started working backwards from the actuators and when I got back to the IWE solenoid, I wasn't getting any vacuum through it. While checking different lines and check valves to see if I had hooked up something wrong, I suddenly had vacuum again. I decided to go get a new IWE solenoid and replace it but wasn't totally sure I was going in the right direction. After replacing it, I have had no more problems. From what I can decipher, the combo of the 2 contributed to my problems. As long as the IWE solenoid was working all was well, but at times it would not work and the leaky check valve would allow the vacuum to drop and then the hubs would try and engage.

Anyway, thanks again and tomorrow I get to try out my newfound intelligence again...my wifes '03 4x4 Navigator is grinding when you accelerate. The way she has been describing it I thought it was a pinging noise upon acceleration. I drove it today and its definately a hub grinding and has been for some time now and it doesn't quit when you put it in AWD or 4x4 high so I hate to know what I'm going to find when I get in there.

 

Your navigator problem might just be a bad wheel bearing. If that's the case you have a fairly easy repair. The wheel bearings just cost some $. Good luck.

 

It would be sweet if thats all it is but it doesn't make the noise except on acceleration or under load. I'll know something in a day or so when I get a chance to check it out and I'll let you know what I found.
Thanks-
Randy

 

Oh, i see, well im not sure how the 4x4 system is on those, but that almost sounds like one of the problems with these IWE systems, if there is a leak in the system somewhere, the vacuum willl get low during acceleration or load and cause the IWE actuators to try and engage. Just another thought.

 

Hey guys, having a problem again with grinding noise coming from drivers front. I replaced both hub assemblies and both actuators last year bout this time and no noise during warmer months. Now at 9 deg outside my noise is back. Just wondering exactly where yall are talking about I can disconnect vacuum line in order to drive without further damaging anything until I can get vacuum tester to figure out if leaking or not. Do you think it maybe my solenoid? I took hoses off solenoid with engine running and they still have vacuum while off is this normal? Thanks for any help!!!

 

On the line coming right off the intake, about half way between the intake and the soleniod is a check valve. Disconnect the hose from the check valve, on the side of the check valve going to the solenoid. Now you need a cap to cap off the check valve. The cap keeps the engine from sucking in air all the time (You dont want that) and unplugging the line repleases the vacuum from the IWE system and allows the hubs to engage. This is fine because there is no grinding to harm anything. You are not in 4WD at this point. all your axles up front will turn cause they are engaged, at the wheels but not at the transfer case. The only thing you will notice is maybe a slight loss in MPG.

This method stilll allows you to engage into 4WD if needed. Because your front axles are already engage. When you turn your 4WD switch on the dash or shifter on the floor the transfer case will then engage to the axles and give you 4WD.

I try not to ramble to much, but does that make sense?

 

Makes sense to me. What should I cap it off with? The only thing that don't make sense to me is why the hell do we have to deal with all this vacuum crap if when you disconnect it your 4x4 still works. Hell I might not ever hook it back up. I'm just really frustrated at this grinding noise and vacuum lines period!!!!! Sorry for ranting on, I'm thinking it may be easier just to replace all vacuum lines and be done with it hopefully. Can get lines from silverstateford.com for bout $53.

 

When i went through my ordeal last year i just replaced all my lines with regular rubber vacuum hose, the bulk stuff from napa, and i ran the hoses in easy to access areas. i probably got all the hose and generic connectors for about $30 i would guess.

The deal with the vacuum system is to free up resistence and allow the truck to move easier and hence give you better MPGs. Because when the hubs are engaged and everything is turning up front, but your not in 4WD, your in a sense pushing the front to turn, putting more resistence on the truck. The vacuum system keeps the hubs disconnected. As long as there is vacuum everything is disconnected, but as soon as you get a leak somewhere (hoses, actuators, check valves) then the vacuum cannot hold and it allows the hubs to try to partially engage.

My truck ran for a minimum of 8 months with everything up front turning before i realized it, i never had the grinding noise, Because the one actuator failed so bad to the point where no vacuum at all could build in the system and the hubs just engaged.

I will tell you though, i did have to re-replace the ones actuator after about 6 months because it was sticking a bit and wouldnt let go completely. So even though you just replaced the actuators one could be bad i guess. There should be a 12 month warranty on the parts (Mine from my dealership did) so maybe you can rip them off and take them in and get brand new ones. Just a thought.