Car is a Saab 9-7 (Trailblazer SS) with the 6.0 V8, procharger, etc. Sounds like bad belt chirp (ree ree ree). Take all the belts off, chirp persists.
Rev it to 1800 RPM, chirp goes away completely, In between idle and 1800 RPM it gradually gets quieter as RPM goes up
Engine sounds healthy otherwise, sounds like noise is coming from passenger side lower, at crank speed (not cam speed) Didnt see witness marks on anything on the front of the engine, didnt pull the inspection cover on the trans.
Any ideas?
Vacuum leaks can make some funny sounds, my dad lost a TB gasket once on a old TBI 4.3, truck sounded like a tea kettle at idle. I've got one now that sounds like a bad bearing somewhere in the accessory drive, except it doesn't stop when the crank stops, it stops shortly thereafter when the vacuum gauge falls to 0.
When the Procharger was installed, was the harmonic damper pinned to the crank?
Any high torque LS based engine, even turbo or very powerful N/A, needs the damper pinned or it will come loose. BTDT too many times to count. Have got much mileage out of the Magnusson-supplied pinning guide.
Had the same thing. Took a while to find the bad PCV valve. Had split and made a squeak/chirping sound at idle.
Knurled said what i was feeling, harmonic balancer, they are known to separate on stock ls, and yours has an extra parasitic drag on it. worth checking.
Different engine entirely, but the front cam sensor on a late 302 makes a very similar sound before failing. The diagnosis is to take the belts off and see if it persists. Don't know if the LS motors have anything similar.
