Start up grinding and IWE?
 

Hey everyone,
I have a 2007 XLT 4X4 SCAB with the 5.4L and 3.73LS. I recently heard some grinding while I was going down the road that disappeared once I slowed the truck down and came to a stop. The sound seems to be consistent with what I have been reading about the IWE issues with these trucks. I also have a problem with grinding when the truck starts up after sitting for three or four days without being used. It almost sounds like a dog barking (Woooff) and then it's gone. It happens as soon as the truck turns over and lasts only about a second. I was wondering if any one though that this might be related to my IWE issue. I was thinking something along the lines of the IWE system losing it's vacuum after sitting and then making the noise when I start the truck after a few days as the system builds it's vacuum again. I have to make a trip to the ship unfortunately since it's still under warranty, but I wanted to get some feedback and educate myself about the possible problem before I go talk to the service department. They tend to blow things off and tell people that "it's normal, they all make that noise" when in fact, there could very well be a serious underlying issue. Any input would be appreciated. Thanks in advance.

The grinding noise is vacuum related, as you know.
The vacuum lines either have moisture in them or a leak.
I had a vacuum line melt basically, so that was my leak.

Behind the knuckle are two vacuum lines, follow them up and see if they are cut anywhere. One of the lines, I believe is a vent and it goes into the engine bay and stops.

I have no idea what the wooff sound is....

Good Luck with the trip to the Stealership.

how about a picture of the vacuum lines your talking about. I have the same noise i think he is talking about or atleast i think is the same. it is only as soon as i turn it over like he said lasts for about a second or 2 and then goes away. sometimes it doesnt do it. I just kind of thought it was kind of normal but...

The grinding I'm refering to is coming from the auto locking hubs (IWEs).
I don't know what the grinding is on engine start up....?

Don't have the truck with me to take pictures.
IF you look, you can't miss them. Behind the knuckle there are two vacuum lines that plug into it.

Also, if the grinding noise starts and you are going slow, you can put it in 4wd and it will stop, then put it back in 2wd. If the noise does stop when you put it in 4wd, the there is a problem with the vacuum lines...moisture or leak.

alright, well i was completely thinking of soemthing different. sorry guys

no idea what the start-up noise is. sounds like your intake...might want to check your air filter and all the parts/peices are tight.

as MBB said, check all of the vacuum lines. and if you're driving and the noise occurs, switch to 4x4 real quick. noise goes away, you have 100% proof there is a vacuum problem. can be the lines are cut/rotted/melted/not attached...or the motor itself sometimes gets corroded out from moisture coming off the hood/firewall.
the system deliberately vents the vacuum when you turn the truck off. the front hubs are always engaged when engine is off. that's why you have to flat tow these trucks and can't do a dolly or tow with rear in air.

on start-up, the vacuum motor draws the inital vacuum...pretty quickly, about 1-2 seconds. this disengages the hubs for 4x2 driving

Where exactly is the vacuum motor located? When I hear the other grinding on startup, it sounds like it's coming from the passenger side firewall area. Do you think that the startup grinding could be associated with a problem with this vacuum motor? It only happens if I let the truck sit for a few days without starting it. JTProuhet, does your truck only make the noise after sitting for a while like mine?

ya like sitting at work, 10hrs or so, it will do it. but it is only when i start it. it never makes any noise when i drive it. Sometimes i dont know if anyone else has this, but if i get in it in the morning, and put it in drive, it kind of shutters for a couple 3-5 seconds and then goes fine. i dont know...

i have the same startup grind after sitting for more than 6-10 hours on my 5.4 expo too. My local shop guy is a pretty good friend, so we took it in one night to take a look, he said there's def a small vacuum leak , and the grind is coming from the vacuum motor after it sits for long periods. The other potential cause on the 5.4s is the timing tensioners bleeding down, and my buddy said using 5w-30 with a oil additive such as lucas oil once your warranty expires will help that problem, without dishing the cash out for new tensioners.

Matrix, Read here for trouble shooting the 4x4 vacuum system;

https://www.ford-trucks.com/forums/8...then-some.html

My recently purchased truck had the problem and I'm schooled up on it now, after having done the repairs myself. The larger of the two lines on the top of the IWE actuator is the vacuum, and the smaller line is the vent.

2-year old thread still has life.

Good catch on the timing chain tensioners. Normally caused by not using the motorcraft FL-820S filter.