Where should I start?? It hasn't run hot but I didn't drive very far after it happened and I ran the heater. Also noticed some very small pieces of trash floating in the antifreeze. Cap bad?? Radiator clogged?? Thermostat?? TIA.
I have seen in the past where not enough water in the system causes the remaining coolant to boil out violently when it hits the hot surfaces inside the motor. Maybe you were too low to begin with? Did it seem to run too warm before the boil over?
The gauge may have been up a little but not enough to worry about. I put the thermostat back in and let it run with the cap off and added water until it was full. Put the cap on and let it run for about 30 minutes and it did fine.