If it is white smoke that you are saying is from your exhaust then it usually means you have internal coolant problems,things like a cyl.head gasket,cracked head/block and another one worth looking at is the E.G.R system where the gasses pass through a cooling chamber.Not sure on your model but they are usually a stainless steel fitting near the EGR valve which leak internally and have had a few diesels with this problem.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.