When I start my truck in the morning there is an intermittent chirping from under the hood. I've had this happen before on another car and it was an idler pulley with a failing bearing. Any tips for diagnosing this at home? There are a couple pulleys (ha) in there and I'd like to know for sure which is starting to go. I'm headed on a week-long Colorado off road adventure at the beginning of next month and want to get it fixed before departing. I'd take it to my indie shop, but if I can swap the pulley myself, what's the point?