Vacuum Hiss Noise from Engine - Possible Characteristic - keywords cam cover hose hummer intake leak mechanical PCV pipe whistle

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

On rare occasions, a vacuum hiss noise may be heard from the top, rear of the engine. Typically, this noise is more noticeable when the vehicle is idling in an enclosed area with the hood up. The pitch of the noise may also change when moving the PCV hose, which may cause it to be mistaken for a vacuum leak.

This noise is due to air passing through the PCV orifice in the cam cover and does not effect driveability or durability of the engine. If the noise is no longer present with the PCV pipe plugged at the rear of the cam cover and no vacuum leaks are present, no repairs should be attempted to eliminate this noise since it is an operating characteristic of this engine/PCV system.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.