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Jeep Wrangler Whistle - YouTube

My 2000 Wrangler TJ has a whistle that's driving me nuts. I replaced the crank case vent hose as it seemed that it would stop if I touched the hose, thought there might be a leak. No dice. I can't tell where it's coming from.

So the whistle starts about 6-7 minutes into driving, worse on cold days, worse if I just went up a hill or came of the freeway, it happens when I let off the accelerator and then will go away if I press on the accelerator. It seems to be coming from the area you can see in the video (which does NOT narrow it much I know).
 

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I have a somewhat similar sound on mine, and it appears to be the belt. (Not quite the sound I expect a belt to make, I know).

Try putting some belt dressing on it. In a pinch, you can also use grease. See if it alters the sound.

Also, check the belt for stress or glazing. (The latter of which is my issue)
 

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I believe it is all stock.

How do I check all the vacuums and hoses? I'm not super savvy with the mechanics but can follow basic instructions :) I just really don't want to pay more money for things that aren't fixing the problem...
 

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Same problem

I have the same issue on my 2003. I replaced the belt and idler, same noise. Like yours it happens when the weather is cold. It is noticeable when I come of driving the highway but will goes away after I drive around town a little while. I did notice that when I put pressure on the power steering hose coming of the pump it would quit (sometimes). I replaced the power steering house because it was seeping anyways. Didn't cure the problem. I have tried to check for vacuum leaks but haven't been able to find any. During this summer it doesn't make the sound. Still trying to find the noise. The engine runs the same whether the noise is happening or not. The hard part is that it will be making the noise after I come of the highway (when the weather is cold) but by the time I stop and try and figure out where it is coming from the noise quits. Hope some one has some better ideas.
 

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I believe it is all stock.

How do I check all the vacuums and hoses? I'm not super savvy with the mechanics but can follow basic instructions :) I just really don't want to pay more money for things that aren't fixing the problem...
The video you linked is a good reference for this exercise. So, looking at where you're air intake runner/tube is connected at the intake manifold, you'll see a large black hose that connects to the round black brake booster. There's one. Now look at the intake manifold itself, near where the brake booster hose connects to the manifold, T which point you'll see other smaller hoses connected to the intake manifold. You'll need to do these checks while the engine is running, at idle, but you must take caution for hot parts, and moving accessory drives at the front of the engine, such as the fan, serpentine belt, etc. As you listen for the hiss or whistle. Try to isolate where the noise is loudest. Shut the engine down and check each hose connection, hose condition (cracks, splits, fractures, oil contamination), and it's ability to seal to each male fitting. At least one hose will have a section of plastic tubing, check them too.

I do not recommend the novice handling a running engine in order to do the above. Nor would I recommend using sprays like WD or carb cleaner around the connections, although it is a valid test for manifold gaskets. There is a hazard involved if you're not familiar with automotive work.
 

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There's also the MAP sensor, the rectangular device that's mounted to the top of the intake. It uses an o-ring to deal its connection, but requires removal for inspection and service.

A factory service manual would be a great investment, also.
 

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My '02 4.0 does the same thing, on colder mornings it'll tea kettle whistle after about 2/3 minutes after i started it(only when I'm off the gas). After about 5-8 min of whistling it goes away completely as the engine is now completely warm. It doesn't come back to the next morning usually. I've always been under the assumption it was my intake manifold gasket as most people who replace it don't hear the sound anymore. I will be replacing it soon
 

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My '02 4.0 does the same thing, on colder mornings it'll tea kettle whistle after about 2/3 minutes after i started it(only when I'm off the gas). After about 5-8 min of whistling it goes away completely as the engine is now completely warm. It doesn't come back to the next morning usually. I've always been under the assumption it was my intake manifold gasket as most people who replace it don't hear the sound anymore. I will be replacing it soon
Yes ^^^

Exact same sounds and fix. Matter of fact... The first day I drove with the gasket replaced... Gas station guy says "where's the jeep"
He would know I was coming hearing the whistling a mile away rofl

Check around the manifold area :thumb:
 

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To pin point the area where whistle is comming from you can use a 3-4ft piece of new gas line or heater hose, or garden hose for that matter. Short 3 ft works good. Put one end up to your ear- start search with the other. You can locate down to a 1/2 inch away-if not right on. BTW if using a piece of heater hose or gas line-if you close to a bad spark plug wire you will throw hose while lighting up you ear. Don't ask me how I know this. Some times you can use needle nose pliers to squeeze rubber vac lines to test. I have heard a few vac brake boosters leaking vacuum in my day that would whistle. hope this helps.
 

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I had the exact same issue.. Mine was the metal fitting going to the top side of the power steering pump, next to the cap.. I figured that out by listening and isolating the area of the motor. Then wiggling all lines in that area. When found That it, it either made it louder or more quiet. so I pulled off the metal nut holding the hose to the pump cleaned it up and reattached. It was tight but apparently not tight enough.. Problem solved.
 
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