Engine whine that stops under acceleration

Dangeruss

Dangeruss

New Member
Joined
Nov 9, 2021
Messages
7
Location
Anderson IN

Here is a clip of the noise. Starts usually 3-5 min after startup at idle. It goes about 5-10 min then noise disappears. After 5-10 min of around town driving noise returns as a quiet sound then builds. Have noticed it stops Under normal acceleration but persists through rpm up at an idle. New alternator and belt 11/2/21. Removed belt and spun all pulleys they all spin free including the fan. This noise will eventually go away after sitting at idle for about 10 min and you must drive it to get it to replicate the noise. I’m pulling my hair out here, I did do a quick carb cleaner to the vac lines and didn’t get any engine rev.
 
It sure sounds like a vacuum leak but video makes it hard to tell. Did you run it without the belt installed and did the sound remain? If you can rule out the accessories bearings then I would look closely at the intake manifold and throttle body to ensure all bolts are properly torqued.
 
Correction that didn’t help. Definitely a vacuum leak but I’ve sprayed the lines I can see and nothing. Engine runs just fine but the noise is crazy
 
Update: have been to 3 separate shops, I’m in this bad boy 300.00 so far in diagnostics. No one has a clue. Had the vacuum lines smoke tested and all minor leaks fixed. Vehicle still whines as loud as ever. Now I’m hearing a possible IAC valve? I’m not excited about taking off the throttle body since I am not positive this will actually fix the issue….I think I need an exorcist?
 
Sounds like a bearing to me. I would try adding a bit of oil to each serpentine belt accessory's bearing area, one at a time. Or, if you can find one, use an old stethoscope with the very end taken off and see if you can pinpoint exactly where the noise comes from.
 
Dangeruss said:

Here is a clip of the noise. Starts usually 3-5 min after startup at idle. It goes about 5-10 min then noise disappears. After 5-10 min of around town driving noise returns as a quiet sound then builds. Have noticed it stops Under normal acceleration but persists through rpm up at an idle. New alternator and belt 11/2/21. Removed belt and spun all pulleys they all spin free including the fan. This noise will eventually go away after sitting at idle for about 10 min and you must drive it to get it to replicate the noise. I’m pulling my hair out here, I did do a quick carb cleaner to the vac lines and didn’t get any engine rev.
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Hey friend.
I had a similar experience a couple of months ago. Check the exhaust manifold bolt closest to the fire wall On the drivers side. Should be a 9/16. Mine was only 1/8 loose. Sound never came back.
 
Quackattack said:
Hey friend.
I had a similar experience a couple of months ago. Check the exhaust manifold bolt closest to the fire wall On the drivers side. Should be a 9/16. Mine was only 1/8 loose. Sound never came back.
Click to expand...
X2. Mine did same thing
 
Start your jeep and let it get up to running temperature. Remove the serp belt and see if the noise is still there. This will eliminate or confirm if it has to with belt driven components.
If its not a belt driven component, the next step should be smoke testing the intake system. Remove the airduct at the throttle body and tape shut the mouth of the throttle body. remove the vacuum hose at the brake booster and introduce smoke thru it.
This will let you see if you have a leak at the intake/exhaust manifold/vacuum hoses/throttle body.
I have heard bad throttle body gaskets make that noise.
 
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