L10 smokes and blows oil

The easiest way to see what is going on, is to pull the whole manifold off. Plug the oil pressure fitting and turbe drain hole, reinstall the turbo crossover to prevent "stuff" from falling into intake, and run the engine for about ten minutes. If you have a problem this will narrow it down to a specific cylinder. From there you will have to identify if it is valves or injector. It could be a cylinder, but doing the simple things are easier. It is much easier looking for one culprit than many. It is possible to have boost leakage past seals of turbo into crankcase. It is rare but I have seen it.

 

Blue smoke is from lube oil entering the cylinder from either valve guides or past the rings.
White smoke can be caused by fuel entering the cylinder but not being burned and being blown out the exhaust pipe.
The 10 minute period from cold startup without popping (I assume out exhaust pipe) indicates a tight exhaust valve adjustment holding the valve off the valve seat after engine is warm. Lube oil also thins and pools on top of the cylinder head in this first 10 minutes after startup and if the valve is held open, oil can enter the cylinder through the valve guide of the offending open valve and cause blue smoke at the stack.
With the valve being held open, you create low compression in the cylinder. The piston rings require compression to properly seat to the cylinder wall. Without compression you will have blowby past the rings and into the crankcase and out the blowby tube.
You could have a tight valve adjustment or a worn out valve guide causing the problem.

 

Now it's sounding like your typical case of liner cavitation where coolant enters both the cylinder and the crankcase through pinholes in a liner. When the piston is down coolant leaks into the cylinder, when the piston is up the coolant pressurizes the crankcase and blows steam out the vent tube.

Drop the pan and look for water droplets coming down the liners. You may have to roll the engine over by hand to get a good look at them.

 

White smoke out the crankcase vent along with excessive blowby could indicate a component overheating in the crankcase (scored hole/burned piston). You can pull the exh manifold and run engine to locate which cyl or go ahead and pull the head to see it.

 

Did you take it to a shop or just called aound?
I always hated to diagnose someone's problem that would probably just fix it himself.
I'd drop it off and have them diagnose the problem. If it's going to cost too much to fix, be prepared to pay them to put it back together or have it towed home.

Have you looked for a used engine?

 

This is one you will have to sort out yourself son. From what I see you don't have a regular workshop to do your maintenance. These other workshops you have gone to don't really want to get involved in a guessing/diagnostic parts replacing scenario....particulalry in a sixteen year old truck. They know it will end in tears and arguments.

I have often seen this over the years where a guy buys a truck cheap and runs it successfully for a while. When he eventually hits trouble,he cannot understand why a five thousand dollar truck can cost twelve thousand dollars to fix. He then ends up fighting with every workshop in a thirty mile radius of him,arguing over repair bills and procedures. You also say you left the truck sit at a workshop for three months awaiting diagnosis? If that happened at our workshop,I wouldn't touch the job with a bargepole. Either the guy has no work for the truck,or he has no money...or even both. If he has no work for it,then it is cheaper for him to hire someone two or three times a year to move his backhoe or whatever he wants moved,whenever he wants it moved. If he has no money....then you are richer to be selling lollipops then working on said same truck.

You need to get a good Cummins L10 mechanic/operator who knows these engines inside out,and get him to look at it for an hour. He will be able to narrow down your possibilities rapidly and set you on the right track. At least then,you can instruct a workshop or an individual to carry out the required repairs,and stay within budget.