94' Honda Civic overheats on corners

My 94' honda civic vx (1.5 L V-tech e) has 230,000 on the body, but only about 60,000 on a rebuilt engine. Will drive and, according to the gauge, maintain a steady and normal temperature while driving on most roads, climbing steep hills at high rpms, idling, but then if I take corners fast, usually going downhill, the needle will steadily climb up, and it wont stop even if I bring the car to idle, or if I slow down, or go straight, most everything has been tried. Coolant: full. Another weird thing: The heater blows cold air during these occurences.

If you stop, turn off the car and let it cool off a long while, it usually is fine again, until you take corners again.

Symptoms: overheating, heater blows cold air, happens around corners, downhill. Overflowing coolant tank.

I have 2 guesses.

1. Junk in cooling syst. Is stirred up by cornering and plugs thermostat and heater inlet?

2. My water pump is shot, and car has been running on thermal updraft, but cornering moves hotter water towards the temp. Gauge?

Thank you so much for you help, I have my cooling system taken apart right now, and I need some advice.