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Old 09-02-2019, 03:00 PM
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Whistling Noise Under the Hood

I've had a whistling noise under the hood for almost two years.

It only happens under the following conditions:
  • When it's cold outside
  • When the engine temp is warmish but not yet the normal 210 running temp
  • When I shift or take it out of gear
  • But not when it's out of gear and I'm standing still
The whistle is an obvious air flow issue but I cannot detect it in the shop.

(I haven't yet been able to get my ears under the hood while someone else is driving.)


Of course I have checked the K&N connections and they are all tight. The whistling started long after the K&N was installed.

Has anyone experienced something like this? Any clues you can give me are welcome.
Thanks.

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Old 09-02-2019, 03:53 PM   #2
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Look for a cracked or loose vacuum line or fitting. With the engine idling spray some carb cleaner at the intake gasket and around the vacuum lines/fittings. Engine idle will speed up when the cleaner is pulled into the engine and burned. Do this before it has time to warm up and close off the leak.

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Old 09-02-2019, 05:40 PM   #3
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When I first got my Jeep it had a whistle/whine noise while driving. It seemed to be RPM dependent. I couldn't duplicate it without the Jeep being driven. It was driving me batty.

I tightened all the intake/exhaust manifold bolts and the noise went away.

Let us know what you find.

Good Luck, L.M.
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Old 09-08-2019, 09:11 AM
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Whistling Noise Under the Hood - FIXED!

Fixed! My two year teapot whistle is gone.

I checked for vacuum leaks with cleaner but found nothing.

The throttle body definitely needed cleaning so I took it out and gave it and the IAC a thorough degrease. It did NOT fix the whistle, but I noticed the whistle was different. Instead of whistling when it was out of gear between shifts, it mostly whistled while in gear just before the upshift for gears 1, 2 and 3. Weird.

When I took the throttle body off the bolts were firm but too easy to loosen. I merely made it a little more firm on the re-install. After cogitating on the whistle change, I figured I'd tighten these bolts some more. The whistling only occurs in cooler weather when the engine is warming up, so I waited until morning when it was 50 degrees and went for a drive... The teapot whistle is now completely gone.

A guy on a YouTube video said he just tightened the throttle body without worrying about the torque spec as it didn't matter. Apparently not. I didn't bother looking up the torque, for my test drive I just tightened it very firm but didn't go crazy.

The throttle body gasket was very thin but in very good shape. Next time I clean the throttle body I'm going to either put in a thicker gasket or maybe two thin gaskets. Then I'm going to torque it to spec.

Torque Matters!
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