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Squeal from serpentine belt or bearing?

henrynhenryn Member Posts: 4,289
edited October 2015 in Buick
I recently (last Friday) replaced the upper intake manifold and the lower intake manifold gasket on a 2004 Buick LeSabre with 167,000 miles. I was helping out a friend who is on a limited budget. The repairs went well, no problems there.

Afterwards, checking everything out, I detected a squealing / chirping from the serpentine belt, so I replaced that with a new Gates belt. I cleaned every pulley, and made sure every one was turning freely (with the exception of the crank, of course).

Now I have a different sound. I have not heard it sitting still, but on the road, when I let off the gas pedal, as the RPMs drop to about 1500 I hear a momentary squeal from under the hood. Only lasts approximately 2 or 3 seconds. Does not happen when accelerating, only when I let off the gas. Can't seem to reproduce the noise when sitting in the driveway, revving the engine. This happens only on the road, only when decelerating. With or without the A/C engaged. The sound is not very loud, and is somewhat low pitched (for a "squeal", that is).

When I was removing the intake manifold, I did remove / loosen one of the braces for the alternator. But it seemed to go back together without affecting the position / alignment of the alternator pulley / serpentine belt. This is by visual inspection only.

Okay, if I may, a second problem. When test driving the car, I observed a "clunk". I first noticed this when sitting at a stop sign, and releasing the brake to take off. My first thought was that the brakes were sticking, and releasing with a “jerk”. Later, trying to diagnose the problem, rolling along at 5 mph, car in neutral, touch the brake and release, the car jerks and clunks. Thoughts?
2023 Chevrolet Silverado, 2019 Chrysler Pacifica

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    imidazol97imidazol97 Member Posts: 27,200
    If you've checked the idler pulley for play and noise, then you left off an o-ring on the PCV valve under the MAP sensor. Open the oil filler cap and see if you've got a large amount of suction there.

    2014 Malibu 2LT, 2015 Cruze 2LT,

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    imidazol97imidazol97 Member Posts: 27,200
    Check for play in the CV joints on the axles. I had to replace mine at 203,000 mi. GM makes things to last.
    You might have a noise in the transmission that you can evoke by turning the wheel. Don't know if that's fixable or worth it.

    Might be missing spring metal spacers on brake pads are missing and letting the pads move. I'd suggest a second set of ears to stand outside the car while someone drives the car and uses the brakes as you describe to get a better sense of the noise. Check the bearings on the struts. Hand on spring while someone turns the wheel with the engine running while sitting on soft surface like grass or gr

    2014 Malibu 2LT, 2015 Cruze 2LT,

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    thecardoc3thecardoc3 Member Posts: 5,767

    you left off an o-ring on the PCV valve under the MAP sensor.

    It's a common mistake and the sound is actually air being sucked in past the rear main seal.

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    imidazol97imidazol97 Member Posts: 27,200

    2014 Malibu 2LT, 2015 Cruze 2LT,

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