Thanks to member "cwmenne"(a fellow Minnesotan) and this thread I decided to take out my radiator, 2004 545i, and clean it as I was going to change my coolant anyway. Here are a couple pics of what it looked like.




I removed most of the loose debris with a nylon brissle brush, then used a shop vac to suck out what I could. There was a lot of sand particles in the fins that wouldn't come out though. Hope this avoids some potential problems down the road.

 

take it to a manual car wash and pressure wash it.

 

Just remember to blow it out the _other_ way that it came in... I've seen people pressure wash radiators from the front - further embedding crap into it.