Egr cooler question

[Paracefan]

I recently went to look at a 2013 T800 with a ISX 450, 220,000 miles. Truck had been sitting 8 weeks without use. The owner told me he had no issues when it was parked but when he started it the day before I showed up it had a check engine light and was 3 gallons low on coolant. He took it to the dealer who pressure tested the system and found no external leaks. The shop told me they expect a bag egr cooler. I returned home. The seller calls me about 4 hours later and says it was only clamps needed replacing, truck is good to go now. 1st question is can this be possible and if it's true how could it not be external? I'm just learning about the egr engines, I have 2007 C-15 now but it's getting old. Any help is appreciated!