[Bruce_MO]

I use a parts grabber… small magnet that’s on the end of a telescoping rod. It’s a craftsman tool I bought many years ago. Some people use a section of old flex cable (like the throttle cable on an old lawn mower) and chuck it in a drill to work down into the water passages to knock things loose. Spend maybe an hour minimum per side pulling out the the chunks and crap. And then blow the passages out with compressed air (wear safety glasses). Get as much as possible, so keep working at it.