My 98 4 cyl. TJ has started to make a pretty loud whistling sound recently since the weather has turned colder.

It's high pitched whistle/squeal when I'm accelerating. It only does this while the engine is cold and stops as soon as I depress the clutch or let off on the gas. And it goes away completely after a few minutes once the engine warms up.

I've checked and ruled out a loose or worn serpentine belt.

It's kind of driving me nutso. Any ideas/suggestions??

 

Are you running a cold air kit?

 

Nope. And no throttle body spacers or anything like that either.
Basically a stock set up.

 

My serpentine tensioner was screaming like a banshee when I first got my 97 2.5 l TJ but $25 later and a new tensioner she ran less noisy. She still ticks when cold and I have to tighten exhaust bolts every now and then but it's a jeep thing.

 

X2 I had to replace a bearing on mine, I have a 99 TJ 2.5L

 

It's not related to the belt or any pulleys.

For the last week or so it's been really nice and above 10C here, and everything has been purring like a kitten.

Today the temperature dropped to near 0C and it started to whistle again. It sound like there is air sucking and I'm losing vacuum somewhere. I also noticed today that when I switch the heater control from "panel" to "floor", there is a pneumatic noise from behind the dash. Happens every time I switch between the two settings, but also only when it's cold out.

Does it make any sense that there would be more of a vacuum problem when it gets colder??

 

Engine fan clutch maybe?

 

Hey Rip, check the vaccum post on the intake manifold. Sounds like one of your hoses may have a pin hole in it. The hole opens when closed and seals up as the temp increases under the hood.

Dan

 

That's what I was thinking when I posted this problem on another site.
Whistling Jeep, suspect vacuum leak - JeepForum.com
Then the sound went away because we had pretty mild weather and I sort of let things slide.
It's started again in the last week or so cause the temp has dropped again.
Now that you've revived this issue on this forum and seem to be thinking the same thing I was, I'll definately be out there this weekend to check for vacuum leaks.
Cheers.

 

I'm pretty sure you have a vacuum leak. I just bought a 97 TJ, and it started squealing as soon as it warms up. I took a piece of flexible tubing and stuck one end in my ear and probed around the intake manifold until I found the noise was the loudest, and I stuck my finger on the manifold at that spot and the noise went away completely. So I stuck a piece of chewing gum on it, and the noise has been gone for over 3 months.

I don't recommend Gum as a fix, I just want to see how long it will last. :) You might use Form-A-Gasket or something, or if it's tubing replace the tubing...You know.

But, that's what I did.