I'm on my third pump. Had mine replaced under warranty with only 5000mi and just had it replaced again at 178,000 mi. I have a hookup at a dealership and it cost me about $600. I do track my car and I believe the second one failed because of multiple dry runs. There is air getting in the cooling lines but only on the track or VERY high loads (full throttle-high rpm for extended stints). The latest pump revision is good and shouldn't fail. Running air through it is about the worst thing you can do to it.
'06 Arctic Metallic 325i | Sport Package | 6MT | Dinan Stage III suspension | Dinan exhaust | 330i manifold swap! Click here!
| Active Autowerke tune | 135i Brake Calipers | Deiselboost caliper brackets | E46 M3 front rotors