If you are getting a lot of white smoke, coolant loss, and actually seeing coolant and not water dripping from the exhaust, then you likely have coolant getting into the cylinders. The actual cause can be many things, but typically its a faulty head gasket, warped head, cracked head, or all the above. The engine blocks tend to be more robust. If the engine has been ran hotter than normal(doesn't mean in the red zone in all cases), then that may be the issue. You'll need to pull the heads, have them checked, etc. If the head gasket is bad, or the heads are warped and repairable(if), you will want the machine shop to redo all the valve seats at that time as well as mill the head to fix the warpage. If it's too warped you'll need a new head.