Loud high pitched Squealing: 454

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SierraDully

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I have a loud high pitched squeal from my big block. I'm thinking it's the water pump going out but I just wanted to get some opinions first.

First thing I did was put in a new serp belt. That did not change the squealing sound.

It almost sounded like a vacuum leak at first. Checked. Couldn't find any leak. But it is loud. Like turning heads a couple blocks down the street loud. It starts anywhere from 4-5 mins after cold starting engine and usually anywhere from 15-60 seconds after hot or warm start. Then lasts till shut down.
It seems to get a little quieter when I get on the throttle. But doesn't completely go away. The engine runs loud anyway so it may be partly covered up by the engine noise. But it's still there. If I'm only 2% throttle and let off completely I can hear the noise get louder when I let off the pedal.
It then stays loud at a consistent pitch when parked. It makes the noise at idle in the driveway or going down the street. It's just not quite so loud when I'm on the throttle at all. After a cold start it may drive normally with no noise for a few minutes before the squeal starts.

With belt removed and turning accessories by hand, there is little to no play in the water pump shaft. I see a small amount of leaked coolant but it looks like it's coming from the thermostat housing gasket. I don't see any coolant in the weep hole.

It's an '88 Dually and has a generator, power steering/hydraboost, a/c compressor (not charged or plugged in atm), water pump and a smog pump running off the belt.
The smog pump pulley feels like there's a little too much free wheel play in it. But I have never heard a smog pump make a squealing Noise like this one. However that's not to say it couldn't be the problem. That's why I'm asking opinions here.

I noticed the auto tensioner is riding pretty much all the way to its maximum tension position. Changed tensioner for another and its in the same position. The belt is old and worn so it may not be quite so far maxed out with a new unstretched serp belt. I have one here but want to source the noise before wasting a good belt.
I have noticed that compared to the crankshaft pulley - directly below the water pump pulley - the water pump pulley is maybe 1/8" offset. I've noticed this before while putting a belt on but it hasn't had issues until now. There is no unusual play in water pump pulley, nor does it make noise when spun by hand. The loudest pulley with the most wear seems to be the smog pump. But I swear the squealing noise is coming from the water pump area.
Spraying with wd40 one at a time does not effect the pulleys or noise at all. I can't seem to do anything to control or alter the noise to confirm its the water pump. Only driving down the street with your foot on the throttle seems to quiet it down.

Any suggestions/ ideas/ experiences welcomed. I should probably do the water pump anyway, but I'm not a fan of attempted fixing before diagnosing.
 

magimerlin

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Take the belt off. Then start the truck. If it still makes noise it ain't anything run by the belt. If it stops making noise it's something the belt runs or the belt(as you did say it's old and tensioner is at max)

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RichLo

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agreed with taking off the belt and running it. if its a vacuum leak, run a propane torch (without it lit) all around everything around the intake manifold. it'll increase idle speed when you get close to the leak
 

east302

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Just guessing that the 454 uses the same setup, but check to see if the power steering pump shaft is flush with the pulley flange. If it’s off, it’ll throw off the belt alignment and make it squeal.

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SierraDully

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Power steering pulley good. Not a vacuum leak. It's one of the accessories. Doesn't sound like water pump. Changed a/c for a dummy pulley and noise still there. Going to change smog pump for a dummy pulley and see if that's the culprit. The mechanic in town said he has never heard a noise like this on a 454 in 30 years of working on them. Hopefully it's the smog pump
 
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