A lot of Coopers are having a very similar issue with not getting oil up there in time and thus it sounds like a deisel truck for a couple seconds, to even a minute or so.... while its a PITA to have to go get all that changed (for free luckily) at least they'll make it right. Till then the overall concensus is to let it warm up for a min or so if it makes the noise, till you get it in for work.
GL