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Old 03-28-2016, 11:17 AM
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Join Date: Mar 2016
Location: Maryland
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Loud Whistle

So I drive a 2001 Jeep Wrangler 4.0L Sahara edition and I have had a loud whistle for the past year now. It is a very loud whistle and I have dealt with it up to this point but now I am tired of it. The whistle occurs after the car has heated up. Once it is heated up the whistle occurs only when I am not accelerating. Oddly enough sometimes the whistle stops on long trips. I think it has something to do with the exhaust. I am taking her in for a smoke test this weekend. Will report back, but if anyone has had this problem before tell me so I can try to get the mechanic to understand what I need done better. Thanks.

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Old 03-28-2016, 11:21 AM   #2
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I believe it is a vacuum leak. Mine does it too

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Old 03-28-2016, 01:19 PM   #3
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Noise is a difficult problem to diagnose on the forum... and often equally difficult in person. We need more details about what you've done to isolate the source.

- Is it coming from inside the vehicle, or outside?
- In the engine bay or the rear of the vehicle?
- Have you moved your hand around inside the engine or cab to try to block the sound? It's amazing how sound reverberates, but you can interact with it by moving around and attempting to redirect the sound waves. You can move your hand around (but not touch anything) and notice if it passes over something that is leaking because the sound will change. Of course, if it's an intake manifold gasket, that's not so easy to do...
- As mentioned, vacuum leaks can make a noise but I usually call that a hissing sound. Sucking air in through a small orifice could cause a whistle if it's the right shape.
- In the case of a loud vacuum leak, it would typically come with a high idle unless it's a very small leak and well-tuned to the audible frequencies.
- We've had a vacuum leak cause the air to stay on defrost because it was on the tubing running through the firewall to the HVAC unit... defrost is the default (no vacuum) position. Acceleration usually causes vacuum to drop, so if your whistle goes away during acceleration that might be a telltale.

Hopefully this gives you some things to try before you put it in the shop... good luck and let us know what it turns out to be.
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Old 03-29-2016, 11:04 AM
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I have not tried the hand thing yet, but the sound definitely is coming from inside the engine bay.I had my friend, who is a mechanic, listen to the sound and he says it is so loud that he has no idea where in the engine bay it is coming from. Fix might not happen this weekend, so the answer to this problem might go another week
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Old 03-29-2016, 11:25 AM   #5
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Does it sound anything like this?

2002 TJ Sport 4.0, 5 Spd, 4.25" Zone Combo, Currie Anti-Rock, Metalcloak Adj Track Bar, 35" Cooper Discoverer MTP's, Dynomax Cat Back
1994 4.0 ZJ
1995 5.2 ZJ
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Old 03-29-2016, 01:33 PM   #6
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Try spraying starting or intake cleaner fluid around your intake manifold where it seals to the head. I had similar problems on my 01 Cherokee and it had turned out to be my intake gasket .. If the motor stutters or the sound goes away while your spraying the intake it's a safe bet you need a new intake/exhaust gasket
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Old 03-31-2016, 11:10 AM
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Correct me if I am wrong, but the cherokee and the wrngler had pretty much the same engine. So how much did it cost you to get it replaced or if you did it yourself how hard was it to do. Thanks.
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Old 03-31-2016, 11:11 AM
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Yes that is the whistle sound, but my doesnt sound so much like a train, haha. It is more of a tea kettle screaming. Its pretty loud like that one is though.
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Old 03-31-2016, 02:17 PM   #9
Knows a couple things...

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Are the engine RPMs normal? A big vacuum leak would cause the engine RPMs to be higher than normal. If the engine RPMs are normal, I'd suspect an exhaust system leak.
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Old 03-31-2016, 04:42 PM   #10
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If noise is similar to video link i believe that is your oil pump drive assembly.
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Old 03-31-2016, 06:22 PM   #11
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I also had a whistle (which would disappear upon acceleration) and it ended up being the idler pulley for the serpentine belt… I kept trying to eliminate sources and since everything was running ok, I sprayed a dab of lithium grease into the bearing area of the pulley and the sound stopped temporarily.

I replaced the pulley and everything has been quiet since.

Just something to consider as a possibility.

Edit: Just listened to that youtube clip, the noise I had was almost exactly the same.


'03 Jeep TJ Sport
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fix , whistle

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