batlin

I think I have also noticed it is much more likely to happen when it is really cold (Under 40 degrees )

ECU Pirate

I have noticed that it appears to have this issue on cold mornings. That being said it will probably be screaming like a banshee tomorrow with temps. projected to be 9.

2resa

I've got the same issue... anything get resolved?

nicksabellajk

Was your radio on when you started the jeep?

rob_engineer

A friend of mine has a 2012 rubi. He had a weird whistle noise he couldn't figure out. Never would have guessed it, but it was coming from the PCV system. The dealer replaced that under warranty and it fixed his whistle noise.

Sierra141

Could it be the water pump going out or , alternator pulley going bad?
Anyone been able to find out?

JKSlow

I know this is an old thread, but I cannot find any resolution to this problem. My JK is now making the identical noise. Only at startup when its cold - absolutely brake related.

Sierra141

Well, I had the same sound and was driving me crazy. The dealer couldn't find the issue, so I decided to look for my self. I found out it was my serpentine belt making the whistle noise upon staring my jeep. I went to the local auto parts store and found serpentine belt conditioner, sprayed a little on the belt and the noise never came back. I did a little research, and people have had a defective belt tensioner making the serpentine belt loose traction and making that high peach noise. I will keep my eye for a bad tensioner, but so far is been good for 6 months.
Also idler pulleys go bad sometimes making a grinding sound while engine at idle. Very easy to replace.

Hope this helps

warpipe

I get a whistle on cold start up too. as soon as I touch the brake pedal, lasts abought 5 seconds. it does it if I brake hard too. I think its a vacuum leak on the booster.