could be an engine mounting or steady bracket with worn bushes causing metal to metal when engine under load [if you try loading engine by leaving handbrake on and release clutch and sort of rock vehicle on clutch-if it still makes noise then as you say it wont be brakes.] dont do it for too long or clutch will overheat!
k
August 2009
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.