How tell if radiator blocked??

[Gene in NC]

How tell if radiator blocked??

May be on third time now on '89 525 172 k running green antifreeze..

First time, sudden oheat after climbing to about 3,500+ ft on way west to Boone NC, and then maybe 10 miles to Boone, on Xmas eve several years ago. Reputable BMW shop did all the routine things before testing cooling system which failed again because of blocked radiator, now easy to diagnose.

Second time two/three years or so later on local run. Didn't need BMW shop to diagnose. I had radiator rodded out and all was fine.

Now, several years later, pinhole blown in gasket on the cover on side of "throttle body". So, is/was it blocked radiator, head gasket, simple coolant system leak at the gasket? Which came first, like the chicken and the egg?

Oh yes, current tells include difficulty bleeding, good compression, but coolant scum on dip tick and oil fill cap.

[632 Regal]

ugly post... why are they clogging? not the normal thing.