2005 Detroit Series 60

check EGR and EGR cooler first

 

I dunt know if one of this may help:

using a soft water , spray all around the engine ( from turbo to air charger cooler to intake manifold, also 3 piece of exhaust manifold rite side of engine block for any leaking air, normally this cause will make u poor mpg, loose power... i do this job every 4 time/year/each unit)
EGR vale will cause black smoke, loosing power, drop mpg. (this part will pop check engine light)
EGR cooler will cause of coolant missing, engine hot too fast...
good luck...

 

Detroits burn leak or use 2 gallons of oil every fuel stop so the coolant loss isn't too bad, no power, its a detroit get used to it, black smoke coming out of the pipes, not making power fuel had to go somewhere, and at 4.2 you won't be getting a bonus this month.

 

Ok here's the deal. The black smoke and loss of power will be directly related to the Charge Air Cooler. If you need a quick way to test this, get some soapy water in a spray bottle, start your truck, spray the CAC and wait for the bubbles. Check the turbo side first. 99% of CAC leaks come from the weld on the turbo side of the truck. Before replacing the CAC ensure that your turbo is functioning properly otherwise you'll have this issue every 3 months. As far as losing coolant, you can run the same spray test on the radiator that you did the CAC. Start there and let me know what you find.