I don't think radiator failure can be related to a specific mileage. It seems to be caused by repeated heat cycles. After many, many times of the plastic being heated and cooled and flexing with internal pressure, it will become brittle and crack. Bad motor mounts will exacerbate the flexing. The additional heat of a V8 will cause it to happen a bit earlier. Cracks are common at the upper and lower hose connections, but can occur anywhere on the plastic, including the side seams. The expansion tank, thermostat housing, and all other plastic cooling system parts may also be the source of failures. Many, if not most, cooling system failures are catastrophic, requiring the vehicle to be immediately shut down and towed for repair. Failure to do so can result in significant engine damage, particularly in the I6 cars. Far too often the first sign of a crack is complete failure.
Considering the risk, most here think it prudent to refurbish the cooling system at 60-80k miles, although my radiator failed at about 50k. Desert heats and a V8 engine appear to speed the process. I am now considering Evans NPG+ in a zero pressure system. It is a lot cheaper than a Zionville radiator.
chiefwej 2003 540i ///m-tech 6-speed
Black Sapphire Metallic w/gray
Last edited by chiefwej; 01-25-2010 at 10:05 AM.