Caterpillar C15 Acert Engine Problems

is the c15 acert engine a good engine. what kind of problems ussually go wrong with them. i am looking at a 2007 international 9400i with c15 cat twin turbo. 512000 miles with full maintenance records. very clean. is this a good engine and truck? is the c15 acert engine a good engine. what kind of problems Caterpillar sued over C13/C15 engine ... ................
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