A real possibility. Silicate drop out sounds exactly what happened to my coolant. What causes the drop out:
These silicates under certain circumstances (coolant with a depleted additive package (worn out coolant), hard water (water mixed with coolant), high coolant temperature, over concentration of coolant (not enough water)) have a tendency towards ?polymerization?, which can cause silicate ?dropout? or ?precipitation? which can lead to gelation of the silicates in the coolant.
See this site for full info:
Radiator Antifreeze Plugging
I am not sure why this happened in my case.
