so I hooked a vacuum pump up to the engine side of the Iwe system and went for a ride. Vacuum goes to 20 inches of mercury almost instantly after startup. At highway speeds there’s about zero inches of mercury on the engine side of the check valve, iwe grinding started at 5-10 minutes into the drive. I moved the vague pump to the other side of the check valve and held ~23inches of mercury (fluctuated a little) for 15-20 minutes of driving, no Iwe noise. I removed the vacuum pump and re assembled the system to normal and experienced Iwe grinding within a half mile. What is going on??? I got home and put the vacuum gauge on the engine side of the check valve and pumped it to 23 inches of mercury and held it for 5 minutes. Completely lost in this.

 

Not sure on this particular problem but I do know some trucks did have a faulty IWE solenoid that would cause IWE issues. It would get wet and cause it to fail intermittently. They had a fix of adding a housing I believe after it was replaced.

 

this is a 2018 I think they’ve fixed that issue, thanks for the reply.

 

One can not expect the check valve and resevoir tank and IWE to hold vacuum for ever if there is no source of vacuum. Let the system pull vacuum then pinch off the vacuum line in different places and see where the bleed off it. Put your vacuum gauge right at the manifold connection before the tee offs, pinch the hose shut and drive the trucks and see if your manifold vacuum actually goes to nothing. Then find and fix your leaks. Before you continue troubleshooting pull the lines and cap going to the IWE because if you continue to keep test grinding them you will destroy your IWE and eventually the front hubs. Also if you have a 4A transmission Ford has never been able to fixe the vacuum system on those trucks and they just perma cap off the lines and keep the IWE locking the front hubs.

 

"At highway speeds there’s about zero inches of mercury on the engine side of the check valve,"

Clear plastic tubing has a tendency to collapse under vacuum and is likely leading to erroneous conclusions. Use vacuum hose.

 

I would say in this case that if the tubing collapsing was the cause it would be when the vacuum is at it's highest level of suck, not when accellerating or at highway speeds when manifold vacuum is at it's lowest.

 

Does anyone know how much vacuum should be pulled for the Iwe system? It seems to drop when the truck is under load, in work if I run the engine up it really doesn’t change that much.

 

The more you open the throttle on an engine and let more air in for combustion the less vacuum that the crankcase produces. Turbo Charged engines are worse which is why the Twin Turbo has a separate mechanical vacuum pump to pull vacuum for the vacuum assisted power brakes.

Engine idle is when there is most vacuum, that is why the one way check valve and the vacuum resevoir to store vacuum while the engine is under heavy load and not producing max vacuum. The IWE will pull reliably at around 15 inches, but 22 in the resevoir is quite common. 7 to 10 inches is iffy and can cause grinding during transition and worse during cold weather.

 

So I think I finally identified the problem. When I replaced the Iwe actuators and all the vacuum hose I got an after market check valve, Dorman brand. I did some vacuum testing this weekend and found that valve was allowing air to move both ways even though it was new. I’m pretty sure that Dorman check valve was bad right out of the box. I replaced it with a ford check valve today and no grinding so far. Moral of the story, buy oem. Fingers crossed the iew nightmare is over for now.

 

I bought the Ford OEM when I fixed mine, then I bought an aftermarket maybe Doorman?? I put both in series if one one way valve is good then two in a row is gooder.