Loud whine and some idling problems?

Tiny
74BOSSK
  • MEMBER
  • 1997 FORD EXPEDITION
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 210,000 MILES
When I start the truck, there is a very loud whining or hissing sound coming from the engine bay. After a few seconds of idling, the idling feels almost like a misfire, but straightens out when moving. When accelerating, the high pitch sound gets quieter and lowers in pitch with the load until I let off the gas, at which point it gets loud again. Once I turn it off, the whine seems to wind down and fade out for a few seconds.
Friday, May 26th, 2023 AT 12:03 AM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,635 POSTS
Based on your description, it sounds like you have an engine vacuum leak. That is the first thing I would recommend looking for.

Here is a link that explains how to locate and repair a leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Try this and let me know if it helps. If you are unable to find a leak, let me know. Also, in the event no leak is found, record the noise and upload it for me to hear. However, what you described is exactly how a leak would react.

Let me know what you find.

Take care,

joe
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Friday, May 26th, 2023 AT 10:44 PM
Tiny
74BOSSK
  • MEMBER
  • 2 POSTS
Thanks for responding. I have to say as I've worked with it I think it most definitely a vacuum leak. So far I haven't been able to find where it is, so I'll just have to keep looking. It just sounds like it is coming from everywhere.
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Friday, May 26th, 2023 AT 11:39 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,635 POSTS
Hi,

Try using carb cleaner as mentioned in the link I attached. It will cause the engine RPMs to change if you hit the area that is leaking.

Let me know what you find.

Joe
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Sunday, May 28th, 2023 AT 1:35 AM

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