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real loud high pitch whistle noise at startup sometimes hmmm

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Old 05-19-2010, 07:57 PM   #1
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real loud high pitch whistle noise at startup sometimes hmmm

well i have never seen or heard this noise ever before on any vehicle and ive been working on them and owning them since 1994, even own a repair shop biz and seen tons of vehicles including these trucks.....and just never seen this before.


and well my 91 recently has developed an odd sound every when i start it up after just having ran it across town real quick.

its a very loud odd high pitch whistle like noise and i cant tell if its coming from under the hood or under the truck by the tranny because by the time i get the hood popped it quits doing it or if i rev it up it will go away within a few seconds usually.


really odd......

right after you fire it up and its running is when it does it, not during cranking time,

wtf could it be?

its annoying.

only thing i can think is an odd vacuum hose or fitting leak

idle is kinda high in the truck now that i disconnected the EGR valve recently in which is the only thing ive changed and yes i plugged off the vacuum hose for it


sometimes it will do it long enough to put it into gear and drive it about 30 feet then it quits.


it only does it after having just run it and when its warmed up fully.

never when cold or first start of the day

weird.,

runs great strong perfect no issues otherwise.

any ideas?

maybe IAC motor is messing up. related to high idle anyways?

i do have a CEL code recently and its for the TPS sensor.

oh its a 4.3 TBI Z and 700r4 and 202k miles almost

we got a 91 full size 2500 pickup today at the shop to replace the dying 305 in and its at 342k miles! i was like holy crap when i saw the odometer today,.

no oil in it and smoking like a train and running like total garbage



done.

new engine will be in soon for it.,

no rust from texas driven up here, couple dents but nothing major, its solid, wow... crazy to see no rust on such an old truck wish my s-10 was like that,..

the only higher mileage ive ever seen is an astro van we had at work about the same year and it was closer to 400k miles still running driving fine but rattly old panel work base model astro van. sold it last fall, still going strong....

these 90s chevy trucks man... i tell ya they do run forever almost, like the old trucks did back in the day..... if the body will stay together.. and frame doesnt rot out..

Last edited by fast68chevy; 05-19-2010 at 08:05 PM.
Old 05-19-2010, 08:18 PM   #2
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Re: real loud high pitch whistle noise at startup sometimes hmmm

my answer is for the title that you gave this thread, not what you wrote in the novel above...uh.... I mean post. my guess is that it could be a belt, because mine did that when it was cold out. I changed all my belts, that ran me about 60 buck for all three, and it hasn't humed since. i hope that helps.
Old 05-19-2010, 08:45 PM   #3
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Re: real loud high pitch whistle noise at startup sometimes hmmm

no this is definitely no belt noise

belt noise is squeaing way different

this is literally a whistle like if you whistle

its some kind of air noise it seems like

real crazy

yeah i typed a novel hahaha

these 4.3L only have one belt

big serpentine


TBI

mines a gator back new

besides this whistle noise is only when its hot and been run already

sometimes the belt does squeal a little when its cold out and humid, in the mornings

but completely different sound, its a chirp chirp chirp for a bit then gone

i think your 86 still has v belts yeah, its old school style still

sucks

ive never had that old of an s10, 91 is the oldest iver ever had all the earlier ones are long gone in the shredder here, rust mosnter killed them all

Last edited by fast68chevy; 05-19-2010 at 08:48 PM.
Old 05-19-2010, 09:05 PM   #4
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Re: real loud high pitch whistle noise at startup sometimes hmmm

Yeah, its definately old school. how hot does it get when it starts to whistle. Because it could possibly be your radiator cap. if your engine temp gets above 212*f then you might be boiling your antifreeze and it could be making vapor causing the whistle. Just a thought.
Old 05-20-2010, 10:50 AM   #5
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Re: real loud high pitch whistle noise at startup sometimes hmmm

Dont worry--put a real loud muffler on it---she sound like ur runnin a big Cummings diesel under the hood, just a thought.

Last edited by rockcrusher; 05-20-2010 at 10:52 AM.
Old 05-20-2010, 06:41 PM   #6
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Re: real loud high pitch whistle noise at startup sometimes hmmm

my old mans dodge car had a similar noise. It was an idler pulley bearing starting to go. Once he replaced that, the noise went away.
Old 05-24-2010, 09:45 AM   #7
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Re: real loud high pitch whistle noise at startup sometimes hmmm

when the tank on my radiator had a small crack in it it would make a whistle sound when the coolant got too hot/ built up pressure.
Old 06-02-2010, 07:51 AM   #8
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Re: real loud high pitch whistle noise at startup sometimes hmmm

I have the exact issue with my 93' 4.3 liter its that high pitch noise that happens on start ups then quits and when its hot out. I've been told its the belt and the idler pulley. i replaced both of those and nothing has changed. My noise it related to the belt in someway because i can hear the pitch of the noise change when i change the rpm. the noise normally happens at low rpm. when i get to cruising speed the noise stops until i slow down.

I dont know if it could be related but i had an engine light come on only when im in park for a minute or two. i checked it and it was the IAC unit. i replaced that with a new one. but i never noticed a high rpm in idle or a low one.

I dont know if the two could be the same problem. but i have been told its my power steering that makes the noise or the compressor but im not going to replace those. I just have to turn my music up a little bit more.
Old 06-02-2010, 02:49 PM   #9
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Re: real loud high pitch whistle noise at startup sometimes hmmm

Air intake might be cracked.. Could be anything but I'd double check to be sure.
Old 06-02-2010, 03:41 PM   #10
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Re: real loud high pitch whistle noise at startup sometimes hmmm

Quote: Originally Posted by Zyme
Air intake might be cracked.. Could be anything but I'd double check to be sure.

when you say air intake are you talking about the plastic big tube that looks like an accordion?
Old 06-02-2010, 08:15 PM   #11
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Re: real loud high pitch whistle noise at startup sometimes hmmm

Yes. It might have a crack in it which could be causing the whistling.
Old 06-03-2010, 10:16 AM   #12
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Re: real loud high pitch whistle noise at startup sometimes hmmm

there is a big gaping hole in the bottom of it but i removed it and still the noise. I figured out if i put it in neutral the noise stops.
Old 06-03-2010, 04:36 PM   #13
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Re: real loud high pitch whistle noise at startup sometimes hmmm

When your in 1st gear does the noise continue? Because when you start your car up it should be in neutral then switch to reverse or 1st.
Old 06-07-2010, 08:34 PM   #14
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Re: real loud high pitch whistle noise at startup sometimes hmmm

I took my truck into pep boys they did a vacuum test. Its the EGR valve thats what was making noise.
Old 04-30-2014, 05:40 PM   #15
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Re: real loud high pitch whistle noise at startup sometimes hmmm

seems to be a fuel injector.. while running if i step on it the sound goes away until the engine smooths out then its back. could be a vac i guess. i think injector because if i unplug one while its running the sound stops.
Old 04-30-2014, 11:02 PM   #16
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Re: real loud high pitch whistle noise at startup sometimes hmmm

ive heard it before, sounds like a idler/tensioner, could also be the alternator. ... pretty much anything with bearings that spins on the serpentine belt system.
Old 05-01-2014, 07:38 PM   #17
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Re: real loud high pitch whistle noise at startup sometimes hmmm

Mine did this when it was super super cold -10f on some start-ups, never figured out what it was, did not worry about it.
Old 05-17-2014, 05:12 AM   #18
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Re: real loud high pitch whistle noise at startup sometimes hmmm

mine doesn't do it at first. seems to take a few minutes. i'll try the belt. should be easy enough..
Old 05-17-2014, 06:25 PM   #19
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Re: real loud high pitch whistle noise at startup sometimes hmmm

Sometimes the pulleys will develop glazing from the belt running and under
tensioned belts will also cause glazing. One has to clean this glazing with
fine grit sandpaper and then clean the pulleys with a good chemical cleaner.
A good wire brush can also be used.

It's important that the correct size belt be used. You'll be able to by the
wear indicator on the idler pulley assy. I only use Goodyear Gatorback
belts.

As well any "chirping" is an indication that a bearing is running out of
grease and be ready with new idler, ac idler and possibly alt bearings
or/and pulleys.

Make sure the belt is lined up properly and in specs with all accessory
pulleys. That's a really big deal.
Old 06-07-2014, 10:31 PM   #20
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Thumbs up Re: real loud high pitch whistle noise at startup sometimes hmmm

1994 Astro 4.3 TBI Z.
Problem=fast Idle & high pitched squeal. Vacuum leak.
I sprayed wd40 near the drivers side base of the Carb-Fuel injector unit where the squeal was coming from.
As the wd40 got sucked into the vacuum leak the engine would miss as wd40 does not burn in the engine. Therefore locating the vacuum leak.
Turn engine off.
I the sprayed something to remove the wd40 so something could stick on the area, I had starting fluid handy.
I applied a liberal amount of rtv gasket sealer on the mounting area right under the throttle mechanism.
The sound subsided some & idle improved some.
I then sprayed paint to finish seal the gasket leak, verses removing the unit & going through all that WITH A $600 BEATER!
It worked, now the idle is normal, the squeal is gone & its painted nicely in that area!

This was not an easy thing to diagnose! I've searched the whole net & nobody had an answer for this problem which seems to be common.

Last edited by hoppedupchevy94; 06-07-2014 at 10:34 PM. Reason: More info
Old 06-07-2014, 11:10 PM   #21
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Thumbs up Re: real loud high pitch whistle noise at startup sometimes hmmm

1994 Astro 4.3 TBI Z.
Problem=fast Idle & high pitched squeal. Vacuum leak.
At higher rpm the squeal went away.
I sprayed wd40 near the drivers side base of the Carb-Fuel injector unit where the squeal was coming from.
As the wd40 got sucked into the vacuum leak the engine would miss as wd40 does not burn in the engine. Therefore locating the vacuum leak.
Turn engine off.
I the sprayed something to remove the wd40 so something could stick on the area, I had starting fluid handy.
I applied a liberal amount of rtv gasket sealer on the mounting area right under the throttle mechanism.
The sound subsided some & idle improved some.
I used spray paint to finish seal the gasket leak(my girlfriend laughed at me when I said I was gonna fix the van with spray paint!), verses removing the unit & going through all that WITH A $600 BEATER!
It worked, now the idle is normal, the squeal is gone & its painted nicely in that area!

This was not an easy thing to diagnose! I've searched the whole net & nobody had an answer for this problem which seems to be common.
Old 07-13-2014, 08:11 AM   #22
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Re: real loud high pitch whistle noise at startup sometimes hmmm

Again, this is NOT a belt or pulley issue. I have the same noise with my 2000 2.2 I have noticed that nothing is broken, or harmed so effit lol unless someone knows or has found out what it is
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