IWE vacuum supply explaination

[fordfreek]

I've been having a problem with my truck ruining the vacuum check valve in the iwe system. I've went through 3 or 4 in the last couple hundred miles . I'm wondering if anyone can explain to me how the device works that the iwe system gets it vacuum from. Being it's a turbocharged engine I'm thinking that this device is supposed to keep boost pressure from ever reaching the check valve . I also noticed that as of yesterday the brake booster is completely empty if the truck sits for 8 hours. Anyone ever have a similar problem? Truck is still under warranty so the dealership will fix it, but I can't get in until the middle of October and I'd really like to know what's going on with it before then. Maybe help get it fixed right the first time. Any info would be greatly appreciated.

 

[fordfreek]

This is the thing I'm wondering about

 

[FordTechOne]

What is the symptom?

These trucks use a valve solenoid and an aspirator in the brake booster vacuum tube; that’s what’s shown in your photo.

 

[fordfreek]

Check valve in iwe vacuum supply line keeps bleeding off vacuum causing the hub to try and engage whenever manifold vacuum is low for a period of time. A new check valve won't last 10 miles sometimes. I have replaced it 4 times and they just keep failing. And now the last couple days all the vacuum is gone out of my brake booster if the truck sits for 8 hours. Brake pedal is rock hard when I first start it. Thought maybe the device pictured may be my problem, just not sure what it does specifically.

 

[FordTechOne]

Check valve in iwe vacuum supply line keeps bleeding off vacuum causing the hub to try and engage whenever manifold vacuum is low for a period of time. A new check valve won't last 10 miles sometimes. I have replaced it 4 times and they just keep failing. And now the last couple days all the vacuum is gone out of my brake booster if the truck sits for 8 hours. Brake pedal is rock hard when I first start it. Thought maybe the device pictured may be my problem, just not sure what it does specifically.

The root cause is not the check valve if you’ve replaced it and the issue is the same. You most likely have a vacuum leak in your IWE system which is causing the hubs to partially engage under low vacuum conditions. The check valve won’t help if vacuum os leaking after that point.

To check for a leak, disconnect the vacuum output line from the IWE solenoid and apply 20 in-Hg of vacuum. If the vacuum drops 0.5 in-Hg per minute or more, you have a leak in your IWE system between the solenoid and wheel hubs.

 

[fordfreek]

Entire system holds vacuum. Already tested that. The problem is that it keeps making the check valve fail. If I go pull the check valve off my truck right now and try to blow through it from the engine side, it will pass air. And now my vacuum booster for my brakes loses it vacuum when the truck sits. I haven't verified it yet because I'm tired of wrecking check valves, but it seems like all I need is one episode of boost and the next thing you know, my hub is grinding. That's why I'm questioning the device in the picture I posted. Is that device supposed to keep boost away from the vacuum system? Turbocharged engines were pretty rare when I worked at a dealership last, which was almost 11 years ago, so I'm kinda behind the times. I apologize if I'm making this more complicated than it has to be.

 

[FordTechOne]

Entire system holds vacuum. Already tested that. The problem is that it keeps making the check valve fail. If I go pull the check valve off my truck right now and try to blow through it from the engine side, it will pass air. And now my vacuum booster for my brakes loses it vacuum when the truck sits. I haven't verified it yet because I'm tired of wrecking check valves, but it seems like all I need is one episode of boost and the next thing you know, my hub is grinding. That's why I'm questioning the device in the picture I posted. Is that device supposed to keep boost away from the vacuum system? Turbocharged engines were pretty rare when I worked at a dealership last, which was almost 11 years ago, so I'm kinda behind the times. I apologize if I'm making this more complicated than it has to be.

The device is an aspirator, the PCM controls the solenoid valve to allow vacuum to reach the booster. According to WSM it is activated when booster vacuum is low to provide additional vacuum. So I suspect it’s normally in the closed position, restricting flow.

This might be a stupid question, but the check valve is install in the correct orientation right? I haven’t heard of repeat failures, that is strange. If the booster is losing vacuum after sitting, that’s either a bad booster (leak) or a faulty booster check valve.

Have you taken vacuum readings at vacuum supply line (from engine) at idle?

 

[fordfreek]

Check valve is oriented correctly. I haven't checked the vacuum before the check valve, but when I was monitoring it going down the road with a gauge tapped in before the solenoid it was running 20-22 inches when the system was operating as it should. So is there a check valve right at the booster in the supply hose , cuz I don't see what looks like an old school one anywhere. My thinking was the two problems were tied together because it was only a day or so after I couldn't keep a check valve in it to save my life that the brake booster issue showed up. Brakes otherwise are normal, no hissing or anything like that.

 

[FordTechOne]

Check valve is oriented correctly. I haven't checked the vacuum before the check valve, but when I was monitoring it going down the road with a gauge tapped in before the solenoid it was running 20-22 inches when the system was operating as it should. So is there a check valve right at the booster in the supply hose , cuz I don't see what looks like an old school one anywhere. My thinking was the two problems were tied together because it was only a day or so after I couldn't keep a check valve in it to save my life that the brake booster issue showed up. Brakes otherwise are normal, no hissing or anything like that.

Yep, the booster check valve is part of what is called the "vacuum harness".

 

[fordfreek]

Ok. Thanks for all your insight. I'm anxious to find out what's causing this strange problem and I'll keep you updated. Unfortunately it's 2 weeks before I can get my truck into the dealer.