Turbo failure on a 2003 320d E46. White smoke suddenly billowed from exhaust and engine cut-out while travelling on motorway. My theory and that of diesel mechanic that stopped to assist on the motorway is that the turbo seals have failed meaning that turbo suffered moderate failure. The diesel mech. recommends a turbo recondition. I am doubtful on a reconditioned unit and also, the question begs to be asked; what other engine items could have failed that may have caused or assisted in the turbo failing. PS. Service where performed reasonably on time and the car is driven mainly motorway.

https://www.oilburners.net/threads/7-3-idi-turbo-blue-smoke.50939/

This may help you.

he causes of white exhaust smoke can vary; however, it is common to see white exhaust smoke when first starting a car, especially on cooler days. This is generally steam caused by condensation. As the engine warms up and the condensation dissipates the white exhaust smoke (steam) is no longer seen. If excessive white exhaust smoke is present well after the engine warms up, it is necessary to have the car inspected for possible internal coolant leaks. Indicators of an internal coolant leak include billowing white exhaust smoke accompanied by a sweet odor or a low coolant reservoir level. An internal coolant leak can also contaminate the engine oil giving it a frothy, milky appearance. Even small amounts of coolant entering the combustion chamber will produce white exhaust smoke.
One of the main causes of white exhaust smoke and coolant loss is a cracked or warped cylinder head, a cracked engine block, or head gasket failure caused by overheating. A cracked head may allow coolant to leak into one or more cylinders or into the combustion chamber of the engine. Dirty coolant, a poorly maintained cooling system, a low coolant level, or a non-functioning cooling fan can cause engine overheating. In addition, engine wear can eventually cause the gaskets to lose their capacity to seal properly allowing internal coolant loss. Intake manifold gasket and head gasket failures are two of the most common sources of internal coolant loss caused by engine wear.
Never remove the radiator cap or coolant reservoir cap while the engine is hot or running as it can cause serious injury; always allow the car to cool down completely first. Checking for a low coolant level in the reservoir is the first step in determining if coolant loss is causing the white exhaust smoke. If the coolant reservoir is at the proper level but excessive white exhaust smoke is present, a cooling system pressure check is required to determine where, if any, coolant leaks are located.

the turbo your mechanic put on was 2nd hand and knackered i expect ,,,,white smoke means turbo still gone ,,,,

It is common to see white exhaust smoke when first starting a car, especially on cooler days. This is generally steam caused by condensation. As the engine warms up and the condensation dissipates the white exhaust smoke (steam) is no longer seen. If excessive white exhaust smoke is present well after the engine warms up, it is necessary to have the car inspected for possible internal coolant leaks. Indicators of an internal coolant leak include billowing white exhaust smoke accompanied by a sweet odor or a low coolant reservoir level. An internal coolant leak can also contaminate the engine oil giving it a frothy, milky appearance. Even small amounts of coolant entering the combustion chamber will produce white exhaust smoke. One of the main causes of white exhaust smoke and coolant loss is a cracked or warped cylinder head, a cracked engine block, or head gasket failure caused by overheating. A cracked head may allow coolant to leak into one or more cylinders or into the combustion chamber of the engine. Dirty coolant, a poorly maintained cooling system, a low coolant level, or a non-functioning cooling fan can cause engine overheating. In addition, engine wear can eventually cause the gaskets to lose their capacity to seal properly allowing internal coolant loss. Intake manifold gasket and head gasket failures are two of the most common sources of internal coolant loss caused by engine wear.
Never remove the radiator cap or coolant reservoir cap while the engine is hot or running as it can cause serious injury; always allow the car to cool down completely first. Checking for a low coolant level in the reservoir is the first step in determining if coolant loss is causing the white exhaust smoke. If the coolant reservoir is at the proper level but excessive white exhaust smoke is present, a cooling system pressure check is required to determine where, if any, coolant leaks are located. THESE LEAKS WILL CAUSE SEVERE ENGINE DAMAGE! Have the car inspected immediately.

I
Internal coolant leaks can and will cause

head gasket

Blue smoke from the exhaust is cause by coolant\water mixing in the combustion chamber. The smoke will also have a sweet smell to it. A simple way to confirm this is to check your coolant level. Also if you take the radiator cap off while the engine is running you should get exhaust fumes coming out since the mixing will be both ways. Although this is not always the case the coolant can mix with the engine oil as well so check that as well. The oil will have a milky brown color to it.
There are several things that can cause this but the most common is a blown head gasket. It could also include a warped or cracked head as well.

This usually happens after the engine overheated for a prolonged period of time.

You should get this taken care of A.S.A.P.
Hope this helps and good luck.
Please let me know if you need anything else.

turbo might of started to **** oil pull off the air hoe to the turbo and see if it is full of oil that will give oyu a place to start looking

Have your head gasket checked you may have a small tear or hole in it allowing coolant/water into your engine internals. This smoke and power loss probably also happens at highway speeds yet is not noticed due to cars momentum

whatch for a clogged crankcase ventilation system. internal crankcase presssure(excessive) will push oil out the turbo shaft seal. also you have a supply line for fresh oil to the turbo and a return line. if the return line gets carboned up and there is nowhere for the oil to go it will push out through the turbo shaft seal.

turbo oil seals will cause a lot of smoking .