DD 15 Using Coolant. Can't Dind Leak.

Pressure in the radiator?

 

EGR leak is the most common cause of disappearing coolant and the first symptom is pressure in the radiator. After it has been run hot, then allowed to cool down completely, run the engine for about one or two minutes. Check the crossover pipe for coolant then. You have to catch an EGR leak at the right time to see coolant in the crossover.

Take an oil sample and send it for analysis. Check for coolant traces in the oil. I assume you have checked to make sure the oil is not visibly contaminated and that there is no volume increase.

Can be a bad head gasket but that usually causes a leak to the outside.
Can leak into the transmission. You would see contaminated oil and a volume increase.
Can leak through a bad compressor. That would be obvious in the oil.
Can be a cracked liner.

A gallon every thousand miles is most likely a bad EGR cooler or a cracked liner. That's a lot of coolant and it has to be going somewhere. If it's not in the crankcase or the transmission then it has to be going through the cylinders.

 

Do the oil analysis first. And did you check the EGR the way I said?

You might spot a crack in a liner with a bore scope. I would start by pulling the oil pan off and pressurizing the radiator. See if any drips happen.

 

Had a similar issue and it was transmission cooler leaking coolant into the transmission. Easy to check, remove the fill plug and if the fluid pours out, you have you answer.

 

Never thought about this one.

I was researching online for a different issue and came across this. Very interesting. Thanks for sharing.

 

It's likely going into your One-Box after side of the turbo. That's not good. It'll destroy your One-Box