SOLVED!!! Loud Screech from the 454!!!

[KendallP]

***EDIT***

Note 1: I believe all videos posted below are a must-view before comment...

Note 2: Belts reinstalled now since they nor the components they run are the culprit.



I picked up the Winnebago from the storage yard yesterday afternoon. Of course I warmed 'er up a bit and then off I went. About a mile or so down the road, I began to hear a bit of a whine. Within another mile or so it became a loud screech... almost a vibrating metal on metal sound.

My first instinct was vacuum because in my mind, the most interesting part of this phenomenon is that it completely disappears for an instant when I stomp on the gas. In that moment, RPMs are changed only slightly. This occurs without fail every time and often more pronounced than my video. See link below...

I removed all belts. Screech still there. Finished up around 10 last night.

Mexicowanderer recommended next I Vice Grip pinch the small hose coming out of the "protrusion" off of the smog pump. So this morning I got up and did that. Then starter 'er up. No noise. Great!

Then I removed the Vice Grips. Still no noise. Dang.

I wish I had starter 'er up first.

So now I'm left to wonder whether the pinch did something or if this only occurs when she's warmed up.

I plan to put 'er back together and warm 'er up with the water pump running again to see if the noise comes back. If so, then I will retry the pinch.

Any thoughts?

Note the noise disappearing for the instant I stomp on the gas...

https://www.youtube.com/watch?v=Rq5XvVMwMVc


New videos...

https://www.youtube.com/watch?v=ImTWQeb8jNE


Upon shutting 'er down after the video above, I noticed another sign. So I starter 'er up again for the following video. Silence until I gave her just a little gas. Then a few more pedal stomps and shudder' down (that's Jefferson State speak for, "Turned the ignition switch to the 'off' position."...

https://www.youtube.com/watch?v=klk4B7nHsjI
.

[Ductape]

Thanks for the update, good outcome.

[time2roll]

More whistle than screech but it is just semantics now that you have fixed it.
Sounded like a New Year's noisemaker.

[braindead0]

Excellent! And thanks for marking this SOLVED..

[KendallP]

SOLVED!

Front carb bolts were both loose. Thank God!
.

[KendallP]

Latest report: Noise definitely increases when I remove the air cleaner assembly and ear localization of that area seems of high confidence

[KendallP]

haddy1 wrote:
That sure sounds like a vacuum leak to me. While hoses are the easiest to diagnose, there is also a good possibility that it is an intake gasket or carb/TB base gasket. I would try spraying WD40 on every gasket surface to see if you can isolate the sound (pitch should change if you spray the leak) and check all of the intake manifold bolts.

THANK YOU!!!

Sure does to me too.

My old man mentioned carb gasket yesterday, as a matter of fact.

WD40 it is!

[haddy1]

That sure sounds like a vacuum leak to me. While hoses are the easiest to diagnose, there is also a good possibility that it is an intake gasket or carb/TB base gasket. I would try spraying WD40 on every gasket surface to see if you can isolate the sound (pitch should change if you spray the leak) and check all of the intake manifold bolts.

[KendallP]

2 more videos added to the OP. I believe they are an important piece of the puzzle.

Sure wish Mex wasn't currently residing in a 5th-world state in the great nation of Mexico in a throwback in time where Al Gore has yet to upgrade their internet capabilities beyond 56k.... MAX!!!

[KendallP]

smkettner wrote:
I could see the acceleration of the cam against the valvetrain to cause a brief silence.
Especially when combined with a worn timing chain.
Or could it be the chain? Not likely to make a screech IMO.
Does the noise seem external and toward the front? I mean you started with the belt driven accessories.
Any access to inspect the flexplate and torque converter?

Noise SEEMS up front, but not positive. Seems more passenger's side and top half.

Not sure about access just yet.

I'm going to post some more videos. I think they could be very telling. I have my thoughts, but don't want to lead anyone.

[time2roll]

I could see the acceleration of the cam against the valvetrain to cause a brief silence.
Especially when combined with a worn timing chain.
Or could it be the chain? Not likely to make a screech IMO.
Does the noise seem external and toward the front? I mean you started with the belt driven accessories.
Any access to inspect the flexplate and torque converter?

[KendallP]

Noise back... and no change after crimp.

I starter er up. Quiet. Revved er up a bit. There it was.

[KendallP]

MEXICOWANDERER wrote:
Big difference between PREVENTATIVE maintenance and BREAKDOWN maintenance.

Am I gonna be be this grumpy if I make it to your age???

Just messing with ya' gramps. You're right, of course. And now I know where all the bolts are when it comes time for a belt job.

Actually the belts were easier back on than off. All of about a half hour. Knuckles in tact and got a good workout.

I Ifeel like I should run er first to see if I can't reproduce that squeal before plugging up that line. Best chance to know if it was really the culprit, right?

[Ductape]

My cam only screeched at low revs, ceased when the oil flow increased. I put off repairs for a while with switching to multi vis synthetic oil.

That was a short range truck. I wouldn't try that going far from home.

[MEXICOWANDERER]

And if performing the necessary acrobatics working in this doghouse to get belts off were a little easier... I might be a little happier about eliminating all of those possibilities when a vice grip pinch might have done it 5 man hours ago!


Yeah the Vice Grips would have found that radiator leak too. Vacuum leak will hiss, squeal or shriek.

"Screeching" implies mechanical failure.

Belt removal and hand spinning driven components is a mandatory inspection service for high mileage vehicles. If you had done this BEFORE the vacuum leak component failure would have been automatically eliminated.

Pack sandwiches and beer. As hot as it is up there, your radiator is not unlikely to do a kamikaze sword dance on the way home.

Big difference between PREVENTATIVE maintenance and BREAKDOWN maintenance.