Perhaps "random" was a poor choice of words....there is obviously something causing it, my bet is on the fan clutch. What I meant by random is that it happens at random times under random conditions. It doesn't happen "every time" I sit at an idle...it doesn't happen "only" on hot days or after a long day of driving or early on first start of the day. Its random as it pertains to the times and conditions. Hopefully I cleared that up without sou.dung sarcastic because it absolutely wasn't meant sarcastically. I know the importance if clarity here and apologize for any confusion. Thanks again to everyone who takea the time.