What is causing the chirp I hear?
Mice under the hood? No. Cummins says this noise is normal and is caused by the engine stopping faster than the belt can. High compression says “whoa” while the fan says “go.” The result is a “chirp” from the pulley. If the viscous fan clutch is “locked up” at shut down, the “chirp” may be heard in the next county. Belt wear and tensioner condition will also determine the decibel rating of your “chirp.
