Need help diagnosing engine sound

Joined
Oct 14, 2021
Messages
11
Location
Boston, MA
Hey guys I’m stumped diagnosing and engine noise. From 17-1800 rpm up to 2400 rpm I get a noise I can describe best as varying pitch ( goes higher with idle) and it’s very much like the sound a length of hose makes when you swing it in a circle. Like a musical whistle almost ? It sounds like it’s coming from under the intake manifold or from the front of the motor. The truck has full power. Not sure if it’s a vacuum leak, or maybe the water pump bearing? Hoping someone has experienced the same thing and can point me in the right direction. Any help is appreciated!

(Side note, would a timing belt make a noise akin to that? One of the bearing in there? It’s quiet at idle no noise. Only happens under increasing engine speed)
 

turdfurguson

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Dec 13, 2017
Messages
71
Location
Nashville
I have used a stethoscope for various diagnostic issues over the years, but I'm doubtful it will be helpful for the sound described. It is more useful for mechanical ticks, knocks, vibrations, etc. Not positive a whirring or vacuum related sound would show up audibly. A bearing going out can sound pretty spooky though at certain speed, and calm down whe rpm increases. You might remove the drive belt briefly and see if it goes away.
 
Joined
May 31, 2003
Messages
9,210
I have used a stethoscope for various diagnostic issues over the years, but I'm doubtful it will be helpful for the sound described. It is more useful for mechanical ticks, knocks, vibrations, etc. Not positive a whirring or vacuum related sound would show up audibly. A bearing going out can sound pretty spooky though at certain speed, and calm down whe rpm increases. You might remove the drive belt briefly and see if it goes away.
I suggested that because OP mentioned bearing.
 
Joined
Feb 24, 2007
Messages
276
Hey guys I’m stumped diagnosing and engine noise. From 17-1800 rpm up to 2400 rpm I get a noise I can describe best as varying pitch ( goes higher with idle) and it’s very much like the sound a length of hose makes when you swing it in a circle. Like a musical whistle almost ? It sounds like it’s coming from under the intake manifold or from the front of the motor. The truck has full power. Not sure if it’s a vacuum leak, or maybe the water pump bearing? Hoping someone has experienced the same thing and can point me in the right direction. Any help is appreciated!

(Side note, would a timing belt make a noise akin to that? One of the bearing in there? It’s quiet at idle no noise. Only happens under increasing engine speed)
My guess is the alternator, mine did “whine” before I replaced it but it would be helpful to have a video to make a better assessment.
 

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