hyperpm

Ok this might sound like a dumb question but idling engine with windows rolled down, I can hear ticking sound every say 5-10 seconds coming from passenger side area underneath car. I get out of my car and look for this strange noise, checked underneath car and it's coming from catalytic converter. It's been cold in Bay Area CA lately... any ideas why my cat is making this noise?

MacGyver

The metal is expanding as it heats up...

hyperpm

That's what I was thinking thanks.