I've read every thread I can find and went over the vacuum diagram and can't find a solution for my problem. The issue is the commonly reported grinding sound coming from the driver side wheel. I feel it's important to add that my truck is just an STX so it doesn't have 4Auto.

I started out by replacing the check valve with the upgraded part #YG360. Nothing changed for me. So I bypassed the system and took it to my dealer. They basically said "good job bypassing it, that's what we do." So I ordered a genuine Ford IWE and left it bypassed until it came in. This is my second truck that I've replaced one of these on so I knew what I was getting into. The one I took off looked fine and just as I suspected, the noise was still there after installing the new one.

Today I decided to try even more troubleshooting. I took all the vacuum lines loose and blew air through them to make sure nothing was blocked. I ran a piece of wire down through the T to make sure it wasn't plugged. I tested vacuum on everything. The vacuum lines all the way from the T near the vacuum pump down to the IWEs all held vacuum just fine. I tested the vacuum reservoir and it held vacuum. I can jack the truck up and put vacuum on the IWE and it releases just fine. I verified that the truck pulls good vacuum when it's running by hooking a gauge up. I don't know what else to check.

The only thing I didn't check in great detail is the solenoid. I did verify that it switches when cutting the truck off but I couldn't verify that it's switching while driving down the road. I seem to remember reading that the computer doesn't tell the solenoid to release vacuum to the IWEs until driving a little ways first.

So I'm hoping that someone smarter than me can tell me what to do next. I'm pretty clueless at this point. I guess my next move would be to replace the solenoid but I doubt that helps either.

 

I did the simple things first like you. I ended up with two check valves in series just for fun. At the output of the solonid where the hose goes off to the IWEs put a tee in the line, connect your vacuum gauge there. Snake the hose out under the hood and tape the gague to the windshield so it can be seen while you drive. After the first start of the day the truck should actually drive for 1/2 mile and then open the solonoid to send vacuum to the IWEs to pull them out. Before I replaced the check valves and had the TCCM update done to give the 1/2 mile drive time to build vacuum. Start engine and vacuum would build slowly and IWEs would start to pull in around 7 inches and grind eventually building to 20 inches and locked in solid. Driving like this over the years and not knowing not only took the teeth off the IWEs but also the splines off the hub to the point that even new IWEs would grind because the hub splines were worn back too far. So IWEs and both front hubs replaced, check valve and bonus for fun valve instaled. All is working well.

These problems get worse when it gets cold, if the IWEs were installed with the idea of if a little grease is good, then more is better the grease can get too thick and cause the IWE transition to be sluggish till it warms up. The IWE at each wheel has a double line, the large line pulls the vacuum and the small line is just a vent to the engine compartment, if the vent like gets moisture in it and freezen when cold then the IWE has sluggish movement also, blow the small line out with air.

Watch the gague taped to the windshield, make sure that as you drive and turn the wheels around corner vacuum does not drop due to a cracked line that only leaks when flexed with the steering.

 

I've thought of adding a vacuum gauge to see what kind of vacuum I'm getting while driving. I find it odd that Ford put a vacuum pump on this truck and it still waits a half mile to begin to unlock the hubs. I'm pretty sure that's an unnecessary step since vacuum ought to be pretty instantaneous after the engine is running.

So did you add an extra check valve in series with the original or did you give each vacuum hose to the left and right sides their own check valve?

 

I put two in series just for fun. The design of the turbo charged engine causes crankcase vacuum to be low, even lower the harder one accel
erates. The external vacuum pump on my 2018 is used just to assist the brakes, not the 4wd system which still comes off engine vacuum and is strongest at idle. I have not researched what the external vacuum pump is connected to on the 2020 model.

 

That makes more sense than what I thought. I was under the impression that the brake booster still got its vacuum from the intake manifold. I'm looking to put together a parts list and go from there. I'll add a vacuum gauge that I can see while driving. Might even use this stuff to add a vac/boost gauge later on.

 

@dan-oz Soundslike you covered things pretty well, good job
Just to be sure, the grinding does sound like this?
How long/miles was it driven with the noise? After everything you've checked, I'm thinking it could be the hub,
I'm assuming by throwing it in 4H the noise stops.

 

http://ford.car-owners-manual.com/f-...-installation/

 

David, where did you get that manual? From what I see there, I like it better than what I have, mine is read only.

 

That is the link that came up. I am one with the Google-Fu

 

Yeah that's the sound I'm getting. It wasn't like that for long before I bypassed the system. Maybe done it on 4 or 5 occasions.