Whistling problem when cold?

Okey for the last couple of weeks my Jeep has been doing this high pitched whistiling when I get about a mile away from my house in the morning. Only does it in the morning or when its been sitting for at least 6 or 7 hrs. It lasts for about 1 or 2 miles then goes away. Oh and it stops when I get on the gas, but only when its in gear. If I put it in neutral and hit the gas the whistle stays the same. Its running fine otherwise, cept for a little stutter on start up when shes hot, but not all the time.

Any ideas? Im assuming its a vacumm leak somewhere, but where? Ive been so busy with school and work I really cant get a chance to look at it. It did it today again, but by the time I found a place to pull over and pop the hood it stoped. Its drivin me nuts! Anybody else have a simalar problem?

Check your power steering pump and serpentine belt tension. I'd bet it's one or the other.

If you can re-create this at idle, you should be able to find it. Pop the hood and fine tune your ear! Kick in the throttle by hand or have a buddy do it. Sometimes a mechanics stethoscope helps isolate noises.

i see your in Pa. out of curiosity, do you have the heat on when it whistles? mine would do this as well before it got warmed up.

No it happens with the heat on or off. And its not a belt whistle its definetly air. The couple times I did get a chance to look under the hood while it was doing it it was coming from the back of the engine compartment. The whole problem with diagnosing it is that I cant recreate it in my driveway. I tried. I have to wait for it to happen while Im driving then hurry and pull off the road.

Oh and it seems the colder it is outside the louder and the longer it lasts.

Thanks for your help guys

Well, I had the exact same thing happen right after I replaced a cracked exh manifold. I suspect mine was an intake leak. It never changed in pitch, only volume.

It happens when you back off the gas due to the high engine vacuum. If goes away when warm because the gap closes once the head and manifold expand from the heat. Mine would stop near idle too since there wasn't enough vacuum to generate the whistle.

I ended up replacing my exh gasket and used high temp sealant on the gasket, as well as the EGR and TB gaskets. No more whistle.

I would suspect a loose intake manifold,throttle body or vacuum hose. Mine did this for years. On time under the hood I thought I would check the intake bolts. They were loose so I tightened them up. It seems to have quited it up some.
Ron

Year? If it's a 97-up, check the canister purge solenoid, the same little nuisance that knocks at idle when it's hot. Mine chirps when it's cold. Just unplug it and see if anything changes. A prime suspect if your whistle doesn't seem to change with engine speed.

Good stuff guys, thanks. I feel pretty stupid for not thinkin of the manifold :moon: Its a Jeep, of coarse its the manifold! lol!

Its becuz the engine is cold and is at high idle. Nothing to worry about. Its the IAC letting in extra air to help support the rich fuel mix of the warm cycle. Thats why it goes away once it warms up.

Some good suggestions above, but also consider your idler pulley........the bearing doesn't like the cold, especially if it has a number of miles on it. Its a relatively cheap and easy replacement (about $26 at Advance).

Fred85 said:

Some good suggestions above, but also consider your idler pulley........the bearing doesn't like the cold, especially if it has a number of miles on it. Its a relatively cheap and easy replacement (about $26 at Advance).

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That's a good point. I've experienced that, and eventually, of course, the pulley stops quieting down, and howls all the time.