Purchased a super reliable vacuum gauge from HF, and got some interesting results that seemed to clash with what I saw on the forum.

First test (more tonight) was to plug the gauge in the end of the line where the IWE sits, so I unplugged the line from the IWE and put it on the gauge.

1. Started with truck in 4a, no vacuum = GOOD

2. While still running turned **** to 2wd, vacuum did not start, after 30 seconds or so I pulled the gauge off and drive the truck forward/backward a few feet and voila we had vacuum. I think this is probably GOOD.

3. Turned the truck off, vacuum level remains for about 5 seconds then drops to nothing. This is what clashed with some of the reading I've done that said it should slowly bleed off. However there's an audible click of something releasing the vacuum so I think this is actually ok.

Tonight I'll apply vacuum to the IWE and see if it holds...

One other thing you can hear in the video is something squeaking as it slows down, after the engine has been cut.

Video of gauge dropping pressure instantly.

 

1. Yes. Good.

2. Never had to move my truck to get vacuum. Mine would be disengaged by the time I got down on the ground to see if the half shafts would turn.

3. Whine sounds like a bearing on one of your fans is going bad. Yes, mine with the new solenoid will release vacuum within 5 seconds or so of turning the truck off.

 

Couldn't hear any noises, but totally normal for it dump vacuum like that. The click you're hearing is the solenoid de energizing, closing off the vacuum port, and opening the vent.

 

Crap....I posted the wrong picture. Ugh

on my 2020, the vacuum line to the IWE is attached to the rear of the intake manifold, and goes to both the brake booster and the IWE check valve.

once the snow clears, I’ll snap another pic and post it.

Since the vacuum line comes directly off of the intake manifold I would assume it will show both vacuum and boost. Might the readings be degraded or delayed because the line is attached to the rear of the intake manifold???

 

This is interesting for me, since I have never even seen an ecoboost engine. Don't the EB engines have a vacuum pump used to create the vacuum for the booster? From the pump, there should be a check valve which leads to the booster, and then through the solenoid and finally down to the IWEs. load a pic when you get a chance, more for my awareness than anything i guess.

The IWEs only take about 6-10" vacuum to operate. Usually i read 20-21" at my booster (5.0L) which is sent directly to the IWEs so they will have plenty of "pull" to disengage.

 

Sorry for the delay posting pics of the vacuum lines on my 2020 2.7

A large vacuum line goes from the rear of the intake manifold to the brake booster. About 10” from the manifold there is a “t” that branches off to a smaller vacuum line going to the IWE.

It’s the smaller line, which is rubber, that I’d like to put a “t” in for the vacuum/boost gauge. I’d tap in between the “t” and the IWE check valve.

so, what you you guys think?????



Check valve at IWE

Line coming off of rear of intake


The whole line....

 

From what I know, the vacuum should have remained when turning off the truck. The solenoid should only be energizing to release the vacuum for 4WD operation of the hub actuators. Vacuum should have remained via the vacuum reservoir and check valves.

 

@Davzog There's no problem teeing off where you're talking. Could you get another photo right where the IWE vacuum line taps off that manifold like thing? I'm thinking I know just what you've got, but I'd need a better photo.

 

Almost. When the solenoid is energized, the vent is closed off, and vacuum is allowed to the IWEs. When it is deenergized, vent opens, and bleeds off vacuum, and closes vacuum to IWEs. It's a little spool valve that moves up/down inside the solenoid.


IWE solenoid I cut apart, sliver object is the "spool" valve. Not a true spool valve, but I don't know what else to call it.

 

Here’s the pic. The IWE line tees of the main line going to the brake booster.