What causes this

[jimson]

Well here is a dumb question I should know the answer too but I don’t. I always want to know why.

A few times traveling the interstate I have seen trucks limping down the shoulder looking for an exit. They have heavy light blue smoke coming out of both stacks. When you go by them the engine sounds nasty rough. Obviously something has let loose in the engine. My question is what?

 

[BillG]

Usually a turbo has quit for the day and the lube oil is going to the intake.

 

[maddog]

DEPENDS??? if it was cold out the fuel lines might be freezing/gelling up

 

[RonG]

In my experience when a turbo goes and you still run the engine the smoke will be black because the engine will be running very rich as the injection pump will be fueling as it was calibrated with the turbo working properly.
These days with electronics in the loop anything could happen I suppose.Ron G

 

[Dualie]

Spit the tip out of an injector, Popped a head gasket and is burning the fuel and oil mixed with some coolant. on the newer trucks it could be a re-gen gone wrong.