Paul is probably correct on this. Go to the firewall near the battery and you will see a valve with heater hoses connected and four screws on top. With engine cold and off, remove the four screws on top and lift up the cover. If it is flooded with coolant above the rubber diaphragm then get a monovalve repair kit. They used to cost about $35. Replace it and see that the cooling system is still full.

Good luck,