One problem related to engine grinding noise has been reported for the 2007 Mini Cooper S. The most recently reported issues are listed below.
While in idle and any rpm, a rattle/growling sound could be heard coming from under the timing chain housing of the engine. When shifting it was harder to place into gear without grinding and very easy to miss a gear when shifting. Master mechanic diagnosed this has a failing/failed timing chain. A new timing chain was installed, costing me $1,400. One week after being fixed the same sound is arising from the time chain housing and need to be taken back in for a new chain yet again. This is not the first time the timing chain has been replaced on this Mini cooper, it is just the 1st while I have been the owner of the car and seems to be an ongoing issue with it.