Vacuum leak?

[BBrinks]

I've been trying to locate what sounds like a vacuum leak for about a month now. It sounds like it's coming from behind and a little below the upper intake manifold, but when I move to the other side of the car to listen, it sounds like it's coming from somewhere else. Same thing when I try to listen to it from underneath the car. I tried to use a vacuum cleaner hose, but still couldn't find it. When it's idling, it sound like it's cycling, it'll whistle a couple times, pause a second, then repeat it. If I raise it to 900-1000 RPM's, it'll just turn into one steady whistle. I thought it might just be air going through the TB, but it doesn't seem to be coming from there.
I checked the vacuum lines from the intake, but any ideas would be appreciated.

Bill

 

[94GTStang]

It's probably your CAI.

If it is a vacuum leak, you might try getting carb cleaner and spraying it down. The motor will bog down due to the carb cleaner getting in. But it won't hurt it.

Or you can take a rag and cover up any leak. That's usually for a leak that is causing low RPM's though.

 

[94GTLaserRC]

I've been trying to locate what sounds like a vacuum leak for about a month now. It sounds like it's coming from behind and a little below the upper intake manifold, but when I move to the other side of the car to listen, it sounds like it's coming from somewhere else. ........
Bill

RC

 

[BBrinks]

Thanks for the replies. I thought it might be the CAI, too, but it started doing it long after I put in a new CAI.

 

[94GTStang]

Maybe you just noticed it. If the car still runs fine, then I wouldn't bother with it. Vacuum leaks usally cause surging idles cause the computer has no freaking clue where the extra air is coming from.

 

[BBrinks]

It's not running rough or anything, it's just annoying. It's about half as loud as a squealing belt would sound. I guess I'll just have to spend a little while to try and figure out where it's coming from.

 

[lvmustanggt]

I have been trying to find vacuum leak for almost year now with no luck. I have change everything but whistle still there. Don't know what to do where to look

 

[red95gtconvert]

PCV valve came loose from the back of the lower intake?

 

[Blackened302]

i, too, was going to recommend you take a look at the pcv valve--it's located in the around you described (in the back of the lower intake manifold, just under the upper).

the carb cleaner idea is a good one, too--found a couple leaks that way myself.

 

[HISSIN50]

Don't know what to do where to look

Try the 5 and 6 year old threads too.

You know you found an old thread when all the original posters are founding members.


Paul's recommendation would have been mine too.

Good luck.