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Possible vacuum leak

Tiny
CHRIS001
  • MEMBER
  • 2001 FORD F-150
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 238,000 MILES
Truck when giving gas the air control doors close and it feels like there's pressure built up. Then when I let off the gas the air flow went back to normal. I was told it was a vacuum leak somewhere. Would a vacuum seal leak do that? Is that a common vacuum seal issue? Also, would a leaking manifold do the same?
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Friday, July 1st, 2022 AT 11:37 PM

8 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,690 POSTS
There is a vacuum check valve #14 for the HVAC system that has gone bad, here is the location so you can replace it and fix the problem. Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.
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Saturday, July 2nd, 2022 AT 5:13 PM
Tiny
CHRIS001
  • MEMBER
  • 44 POSTS
Also, with the issue I noticed poor performance and somewhat of a surge in speed at times when driving also when starting up I hear a tick and on the left side of the engine I hear the leak and there sits two black looks like valves one on each side sounds like the noise is up in there still think it's a check valve rather than a manifold?
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Saturday, July 2nd, 2022 AT 7:36 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,690 POSTS
Yep, there is an exhaust air injection check valve that rott out all the time, it is a common part which you can get at the local parts store, and it can cause the engine runnability problems as well. Upload a pic if you can so I can be sure.
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Sunday, July 3rd, 2022 AT 12:17 PM
Tiny
CHRIS001
  • MEMBER
  • 44 POSTS
Sounds as if the leak is coming from this area, I'm not sure what those 2 black pieces are with a cap on top. They have 2 tinny vacuum hose on bottom and a plug in on top.
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Sunday, July 3rd, 2022 AT 12:29 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Yes, those plastic lines break all the time, use a piece of windshield washer tubing to reconnect the tubing. Move the lines around to find the broken one.
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Sunday, July 3rd, 2022 AT 12:34 PM
Tiny
CHRIS001
  • MEMBER
  • 44 POSTS
Well, I took it to get it looked at and the guy half way did it and said come back well holidays and all he said he thought something to do with EGR valve as well. So, he bypassed that but I noticed on the 2 pieces I showed in the pic the first one had one line running to it and the second one had two lines. How should the little lines be set up? Should they both have 2 small lines running to them? I hope that made enough sense for you to figure out what I was asking. Oh, and thanks for your help your already leading me in the right direction.
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Sunday, July 3rd, 2022 AT 12:45 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,690 POSTS
They don't show vacuum line diagrams for some reason. You might have them on the hood or core support of the truck. If you take more pics and upload them I can try to walk you through the problem.
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Tuesday, July 5th, 2022 AT 11:49 AM
Tiny
CHRIS001
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  • 44 POSTS
Okay, so, I found one issue the line was hooked up wrong fixed it still losing air compression somewhere have to further investigate when I find anything new out I will let you know. Thanks Ken.
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Wednesday, July 6th, 2022 AT 7:11 AM

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