Its the sound of a flat tire. With air coming out. This is what i'm hearing coming from the engine.
Yes Vacuum Leak i had another car before i got my J and was the same thing popped a hose/connection back on and bam the sound was gone.
Check the power steering fluid level.
Peter
'06 Cobalt ss/sc W/G85 Package
Gm Stage II W/2.79" Pulley
K&N Drop In Filter
Custom Magnaflow Dual Exhaust
isn't power steering more like a whining sound accompanied by a very difficult to turn steering wheel.
yes to whining but not always hard to turn only if its really low it will start making noise before it is low enough to make it hard to turn. if it sounds like air it probably is air i would say if you are going to have a hard time finding the leak just get silicon lines. they arent expensive and you pick a cool color to add like 10 hp. but seriouslt if i had a vaccum issue thats what i would do. then you most likely wont have a similar problem again.
