gbkd80

My XJ will start whistling when I let off the gas at highway speeds and after the truck has warmed up. If I press the accelerator, the whistle is reduced (in other words, the whistle follows the accelerator motion). In the video, if the whistle goes away I’m giving it more gas.

I read some things that mentioned it could be a crack in the intake manifold or a vacuum leak... this sounds like it is literally coming from behind the climate controls. I haven’t taken anything apart yet. It doesnt follow the fan or any of the controls (if could be off and still do it).

dave1123

I couldn't hear anything on your video, but it could be either the vacuum supply hose to the mode control or even the control itself.

gbkd80

You can't hear it? weird... maybe it's in that frequency where some people can't hear. LOL, I'm probably like a dog

I did replace the control a while back when I was diagnosing what I thought was the selector not functioning, but turned out to be a break in the vacuum line near the battery. I'm trying to think of how to diagnose this; put the other control back in? Take the control out altogether and observe what happens at highway speeds?

IF the vacuum supply hose is cracked, is that a B to replace?

Ralph77

I heard it no problem but don't have a clue. LOL.

papablista

It is a vacuum leak, is it louder inside or outside the XJ . If inside it is a line to your heater controls,if outside get a piece of hose hold it to your ear and listen all around the engine, it acts like a stethoscope. When you get close to the loudest whistle spray a little brake cleaner or wd40 around it and listen for a change in the rpm . (starting fluid works best but alot of people are scared to use that) , But not me it makes the biggest change in rpm and I ain't skeered.
Found this under your post might give you an idea what to look for.... Good Luck
https://www.cherokeeforum.com/f2/hva...-lines-249375/

gbkd80

It definitely sounds like it was coming from behind the center console area / climate control. The problem is it only happens once the truck is up to temp, and at highway speeds (usually). I'll hear it start a little, and then letting off the accelerator will make it scream. Playing with the pedal also plays with the amount of whistle. So I was in the drive thru line today getting my coffee and decided to pull the console cover off and unscrew the climate control on the spot. I let it hang out and so far haven't heard anything. I did take a close look and where the vacuum line grouping mounts to the back of the module, may not be seated firmly. But there is nothing to lock that in place except two snap ring-type things that keep the rubber seated up against the back of the inlet. Guess we will see next time I go on a long drive...

bluejeep2001

I couldn't listen to your video but my 01 would scream whenever I let off the gas. it would do it while idling sometimes then go away after several seconds to a minute. I was pretty sure it was coming from the throttle body itself. mine was coming from the engine compartment but the high pitch sequel was hard to isolate. I changed the throttle body and put 2 gaskets under it and it seems to have been totally eliminated. I assumed it was bad butterfly shaft seals