Vacuum Leak?

DFOSTER90

MEMBER
2001 FORD EXPEDITION
4.6L
V8
2WD
AUTOMATIC
150,000 MILES

I keep getting a DTC for a small vacuum leak, but the truck seems to be running fine. Only place I have found a leak was in the A/C vacuum line that goes to the vacuum reservoir, and I repaired that. Is there any other common area where there is a vacuum leak or do you have a diagram of the vacuum lines? Thanks

Friday, July 25th, 2025 AT 7:29 AM

5 Replies

KEN L

MASTER CERTIFIED MECHANIC
54,137 POSTS

Yes these engines had a problem with the PCV hose, you need to remove it to inspect. The hose falls apart internally. Here is a video to help find the leak as well, the machine is $65.00 on Amazon.

https://amzn.to/4f8Jqt4

and the video:

https://www.youtube.com/watch?v=LRKWV4Are5c&t

Check out the images (below). Let us know how it goes.

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Friday, July 25th, 2025 AT 12:39 PM

DFOSTER90

MEMBER
3 POSTS

Okay. I will take a look at it. The DTC is P0442 by the way and this is what the scanner reads.

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Friday, July 25th, 2025 AT 1:11 PM

KEN L

MASTER CERTIFIED MECHANIC
54,137 POSTS

Okay, this is not an engine vacuum leak.

DTC P0442 - Evaporative Emission Control System Leak Detected (Small Leak)

So, I would check the gas cap O ring, this is a common place to leak. Next, check the EVAP lines from the engine to the fuel tank, and finally if you can find the leak use a smoke machine here is a video to help show you, I have seen the charcoal canister crack and give this code.

https://www.youtube.com/watch?v=LRKWV4Are5c&t

You can get one for about $65.00 from Amazon.

https://amzn.to/4l1c2px

Let us know how it goes.

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Friday, July 25th, 2025 AT 1:25 PM

DFOSTER90