"What's With The Birds Chirping?"

[Carimbo]

"What's With The Birds Chirping?"

This is what a friend asked after I started the car. She thought (kidding) that there were birds under the hood. Now I wonder, what makes the chirping, louder and more when cold. It's NOT belts, idler pulleys, alternator bearings, etc. Did somebody explain it once as leakage past the rings?

[asavage]

Bet me. It's the alternator belt. Don't believe me? Loosen it up a bunch, start it cold.

[Carimbo]

No need to bet. BTDT; already had the loose alternator belt during cold weather-- that was a blood-curdling screeeech! Especially after a difficult start attempt.

This is short chirping at idle. Cute.

[83_maxima]

Alternator belt.

Mine squeals harder when it is cold and I need to Glow the plugs longer / cycle them more.

[Carimbo]

Yes, tightening up the alternator belt quieted down the birds nicely. Actually Al did it, during the rear main seal R/R session. I had tightened it a few times previously, evidently not tight enough. Glad I didn't bet.

[asavage]

I read that some new diesel alternators are shipping with one-way overrun clutches in the alternator's sheave, specifically to reduce this noise, esp. on shutdown (think the B-series Cummins in Dodge trucks).