I just replaced the intake manifold on my 2000 sle. Everything went fine (or so I thought). The next day I was driving it and it started to squeal when I would let off the gas for about 10-20 seconds and then stop until I accelerate and then let off the gas again. It only squeals during the deceleration until the rpms finish falling and steady out. If I let the car cool down a bit, it stops doing it until it is driven a while again. It takes about 40 min of driving before it will do it, but now everytime I drive the car for a while and let off the accelerator, it squeals. It sounds like the belt, but that is not it. Once it starts to squeal, I can remove the serpentine belt and it still does it. Once the squealing starts, it also sounds like a can of marbles rattling around. The sound is coming from the water pump area. I thought it was the water pump at first, but if it keeps doing that after removing the belt, it can't be it. I also replaced the water pump and belt tensioner before I wised up and checked it with the belt off. Any ideas here? I just bought this car a couple months ago because I was sick of repairing my Z34 Monte Carlo all the time - Funny how this has worked out.

Check to make sure the pcv is properly... pressure blowing by can make the do funny things.

how sure are you that it is coming from the belt - area.......... it seems unlikely to be coming from that area if it happens with the belt off the car is it possible to get a better idea of location of the origin of the sound?

I am just going by where I hear it with the hood open. The "marble" sound is strongest right around the water pump/center of the engine area. The squeal I am not sure where it is strongest other than it is from the passenger side - because the noise is less when I am over by the throttle body playing with the rpms.

i would go with bill on this one, there isnt much on that side of the engine to make noise but the PCV valve.. how is the driveability...? do you have a check engine light? any hesitation issues since this began?

Ok. I'll check it out. No check engine light or driveability issues. Other than the noise, it runs perfect.

Have you turned all pulleys by hand while you have the accessory belt off to check for any unusual squealing? Obviously the sqeal symptom only occurs during decel or coast down, force dynamics are changing all along that accessory belt path on decel. This is just a thought. My $.02

Thanks guys, it was the pcv valve. Now if I had only found this site earlier....

make sure you stick around a while

Reading this morning..before getting to Marks pulley suggestion, I thought...tensioner??

Both pcv and tensioner are the most likely culprits at that side of the motor. I remembered a post about the whistling of a PCV.

Glad you were able to get it fixed up. Hanging around and reading other'* issues is a great way to educate yourself on things before they happen to you. Hope you stick around for a while.