BCURRY06F150

Remember what I posted the other day? Now mine is doing the same thing as yours now, it gets louder as speed increases and seems to be both wheels now. I checked that only the rear tires spin when in 2 wheel and I pulled the vacuum hoses off the Hubs and there is suction. Let me know if you figure any thing out. I will keep researching and let you know as well.

BCURRY06F150

I have checked all 3 one ways and they all seem to work. I did notice when I pulled one off there was a little drop of brown water in side. And does any one know how much vacuum the lines at the hubs are suppose to pull? It is enough to stick toy finger and feel but it does not seem like a hole lot. Any help is appreciated. Thanks.

Dusterdude72

Mine also does not feel like much vacuum (testing by finger suctions anyhow) but that's normal...and its all functioning properly with the switch also.

I found this on a thread about IWE operation " A healthy engine will produce at minimum 17" of vacuum at idle at normal operating temperature. It takes only 7" of vacuum to disengage a healthy IWE." So if the engine produces 17"....then I am guessing that by the time it down sizes in line size and goes through solenoid and such and feeds off to both IWE's that the line ends where they connect to the IWE's is probably a much lower number.

Also I have seen mention a couple times of there being 3 one way valves but I have seen on quite a few threads that there is only 2 one way check valves. including this diagram I found (picture below) . Just figured I would mention that.

Temps are in the negatives here and we have lots of wind and snow so I am not going to tinker with it yet. but when the weather breaks and I get the chance to look it over I will report my findings...but I am guess its going to end up needing a new IWE...we will see.

BCURRY06F150

I found 3 on mine 1 was where the line T's off the brake booster then you follow that over to the where the line reduces ant there is another one, then the hose goes into the solenoid at the top and back out at the bottom then shortly after is the third check valve. Now mine is a 07 so earlier years may be different but that is what I found.

Murray8503

I have a 05 that is doing the same thing. Dealership is replacing passenger side IWE. If I cycle it in and out of 4 wheel drive a few times or drive it for a little bit it goes away. Weird thing is I noticed it seems to only be doing it when temps are below freezing.

EBC-150

My truck is an '05 and has the same 3. The first one is 1/4" to 1/4", the second is 1/4" to 1/8" and the third is 1/8" to 1/8". My truck pulls over 20" vacuum at an idle, but the IWE's were still engaging under low vacuum conditions (in 2WD). If the checks and storage tank aren't working properly, the surplus vacuum will 'release' back into the engine, regardless of what your vacuum readings are. As a result the IWE's will engage (even slightly), until enough vacuum is built back up to disengage them.

P.S. The posted diagram is for the 4.6L. On the 5.4L the vacuum T's off the brake booster (as mentioned). This is where the first, larger check valve is located.

BCURRY06F150

Very true I think all of us with the issue have been subject to the fridged temps may be the problem will go away when it warms up a bit. May be the the IWE vacuum pump can not produce as much vacuum when the air is this cold because of the density?

Dusterdude72

Hmmm...everything on my trucks vacuum system has been untampered with and I didn't notice a check valve at the brake booster... Could have swore all that was there was a standard fitting to port to the IWE vacuum line. Then again, last time I looked all that over it was -35 degrees with windchill so I could have not paid enough attention as my mind was elsewhere haha.

And yes I am sure it all is weather related being that my truck didn't give me any issues up until the start of January when we started getting really cold temps.

I believe I fixed the original issue (IWE solenoid). And now the current issue is a result of the first failure.

I'm sure my vacuum is all working properly and I believe the issue is with the IWE ...likely the drivers side. But again I will know more when I have the chance to look at it. Right now we are getting snow dumped on us again!. And it's blistering cold again!. Hopefully within the next week the weather will be more cooperative.

In the meantime I'm avoiding driving it and if I do I will drive in 4x4 anyways. Because I don't want to make the issue worse and cause any damage.

I'll report anything I find. And anyone else with a similar issue, if you run across the fix then be sure to update us on what you found!.

luvf150

If what you say is the fact.. may be we would need a TSB !!

Dusterdude72

There is no "vacuum pump". The engine creates the vacuum as it runs. And the engine supplies vacuum to the brake booster and t's off to the IWE vacuum line. I don't think the temps have anything to do with changing vacuum output. My brakes still work excellent and the boost has a higher vacuum demand than the IWE's do.

If anything it would be an issue with moisture in the vacuum system freezing and obstructing the lines and the volume and flow of vacuum. That is if the issue is related to moisture (which I don't believe is my issue but is possible for others having problems with their 4x4). But I seen no evidence of moisture in my system when I last inspected in and I also blew the system out for safety measure during the IWE solenoid install (if you do this be careful how you do it so you don't back feed air at your check valves and such or you could cause damage.