Do I have an intake manifold leak?

[LuckyTJ]

Hoping for some more experienced folks to chime in and confirm what seems to be an intake manifold leak? 2003 TJ with 4.0. Whistles at start-up (in Michigan winter) and starts to quiet down at running temperature. Whistle changes with revs. Sound seems to come from the front of the engine, so I first thought fan or water pump or similar...

Water pump, belt, fan clutch are all new within the last 6 months.

I’ve checked all manifold bolts and found one a bit loose, but most were tight (and rusty of course). Are there any other items I should check before resigning myself to removing the intake/exhaust manifold and checking for cracks? replacing the gasket? What should I do next to diagnose?

 

[strumble8]

Find a sensor safe carb/fuel injector cleaner, with the engine at idle spray lightly around the area where the manifold meets the head. If you hear any change in rpm that will indicate a leak. At that point you will need to determine if it’s a loose bolt, bad gasket, or a crack in something

 

[CodaMan]

What do you mean by the "Whistle changes with revs"? An intake manifold leak would be a vacuum leak and vacuum pretty much goes away as RPMs go up.

 

[CodaMan]

Are you sure it's not the idler pulley or the tensionier pulley?

 

[bourbon]

had that exact same issue with mine about 3 months ago, exact same sound. tighten the bolts on the intake manifold. i was lucky and it was the one in the front. whistle went away and has not been back, but on another jeep that someone owns near me had to replace the gasket to fix the issue.

 

[LuckyTJ]

What do you mean by the "Whistle changes with revs"? An intake manifold leak would be a vacuum leak and vacuum pretty much goes away as RPMs go up.

Meaning I can change the pitch by pressing the gas, and when I give it enough gas (vacuum drops) the whistle goes away. The attached video explains better than I.

 

[LuckyTJ]

had that exact same issue with mine about 3 months ago, exact same sound. tighten the bolts on the intake manifold. i was lucky and it was the one in the front. whistle went away and has not been back.

Did you find the bolt loose or did you spray some PB Blaster or similar and tighten bolts that already felt like they were solid?

 

[bourbon]

Did you find the bolt loose or did you spray some PB Blaster or similar and tighten bolts that already felt like they were solid?

found the bolt loose. it was about a turn and a half loose. then i went ahead and snugged up the rest of them just to be sure.

 

[LuckyTJ]

found the bolt loose. it was about a turn and a half loose. then i went ahead and snugged up the rest of them just to be sure.

Rats... I found one loose in the back, tightened and checked all the rest. All seemed tight, but the whistle remains.

 

[CodaMan]

The leak could have blown out the gasket so tightening may not seal it.

 

[CodaMan]

Replacing the gasket, if that's what it is, is a pretty simple job. My one piece of advice is to spend an extra 30 minutes and drop (lower) the front fender and remove the wheel. This will give you direct access to all the bolts and help you get the manifold seated properly on the pins. That 30 minutes will save you much frustration.

 

[LuckyTJ]

The leak could have blown out the gasket so tightening may not seal it.

Seems likely. Is there a general consensus for a replacement gasket? Brand, type, etc? Fel-Pro? Mopar?

 

[CodaMan]

Seems likely. Is there a general consensus for a replacement gasket? Brand, type, etc? Fel-Pro? Mopar?

I used a Mopar

 

[03coloradowrangler]

sounds like alternator whine to me.

 

[williambmac]

Are you sure its not the throttle body.
I've seen them leak around the throttle shaft and at the base, causing your noise.

 

[LuckyTJ]

So, after much analysis (and quite honestly a general dread of having to remove and replace the intake gasket as I'm sure those bolts haven't moved since the TJ rolled off the line), I looked into the various pulleys- belt tensioner and idle... Both came up in my on-line searches as possible culprits and both looked original. I replaced both and that seemed to stop the noise. I SWEAR it sounded like more of an air whistle than a whine though... I'll know for sure next winter when the temps drop again. I'm sure I'll get to do the intake gasket on another day.

 

[03coloradowrangler]

my alternator sounded like a ufo taking off during cold winter temps, shortly after spinning for a bit it stopped the noise. pitch would change with the throttle position. bearings were bad im assuming. replaced the alternator with a new Denso and no further noises ever occurred.

The first time I heard it temps were in the negatives.

 

[StarterKit]

So, after much analysis (and quite honestly a general dread of having to remove and replace the intake gasket as I'm sure those bolts haven't moved since the TJ rolled off the line), I looked into the various pulleys- belt tensioner and idle... Both came up in my on-line searches as possible culprits and both looked original. I replaced both and that seemed to stop the noise. I SWEAR it sounded like more of an air whistle than a whine though... I'll know for sure next winter when the temps drop again. I'm sure I'll get to do the intake gasket on another day.

Hello, how is your Jeep looking in 2023? Any whining noises since then? Facing similar issue.

 

[LuckyTJ]

Hello, how is your Jeep looking in 2023? Any whining noises since then? Facing similar issue.

Mine was apparently either the belt tensioner pulley or the idler pulley. I replaced both at the same time, so I'm not sure which was the culprit. But after that repair the sound (shown in the video) went away and has not returned. The replacement of the pulley(s) was relatively straight forward. I'm sure easier than replacing the exhaust manifolds... It's been a while, so I can't recall which one, but I do remember one of the pulleys not turning as easily as it should and sounding a bit 'crunchy" when I removed it and spun it by hand.

 

[StarterKit]

Mine was apparently either the belt tensioner pulley or the idler pulley. I replaced both at the same time, so I'm not sure which was the culprit. But after that repair the sound (shown in the video) went away and has not returned. The replacement of the pulley(s) was relatively straight forward. I'm sure easier than replacing the exhaust manifolds... It's been a while, so I can't recall which one, but I do remember one of the pulleys not turning as easily as it should and sounding a bit 'crunchy" when I removed it and spun it by hand.

Thx. I am looking at Mopar for parts replacement, i have both the intake manifold and the pulleys YT saved and the pulley replacement is definitely much easier ha. One thing i’m confused about is why does the engine need to warm up before that sound starts and why is it based so much on how you push the pedal? What do pulleys have to do with this? Who knows. Thx for the update though!