Without looking up the exact mileages, it was happening every 10-15k miles. The old design was a fin and tube radiator. The tubes would eventually rupture due to stress. The new design is a bar and plate design which seems more robust. (Fingers crossed). One other item that I forgot to mention was a cracked exhaust manifold at around 60K miles. This seems quite common on the ISB and ISC engines. As far as power, it is not an ISX for sure, but there is no mountain that you won't get over. I typically tow a Jeep Grand Cherokee about 5K lbs, and a Toyota Camry 3K lbs.(not at the same time of course), and you can definitely feel the weight difference, but I can usually keep up with a loaded 18 wheeler. So as long as you are not attempting to break any speed records, it does just fine.
