SMOKE and RATTLE

right the exhaust started to rattle the other day thought it might of been loose but its in side the exhaust middle of the car just under the front doors, the 2nd cat i think and now tonight white smoke started to come out, any ideas what this could be?

coolant burning in the cylinder, could be blown head gasket, or a cracked cylinder head get a pressure test.

[quote author=keith dublin link=topic=31141.msg358610#msg358610 date=1312102755]
coolant burning in the cylinder, could be blown head gasket, or a cracked cylinder head get a pressure test.
[/quote]
yeah i was thinking that but the rattle is coming from the 2nd cat so hopefully its this thats causing the smoke