Two things I can think of. One is the thermostat is stuck closed. Or blown or cracked headgasket or cylinder head or cracked block.
TO check for a blown headgasket let the engine cool. Top the coolant off. Then start the engine watch the coolant recovery tank while the engine is running does it start to bubble or geyser out of the recovery tank after 5 to 10 mins of running and its worse when increasing engine speed? Thats a sure sign of a blown headgasket or cracked cylinder head or block. Also the engine oil will look like chocolate milk shake on the dipstick or when you loosen the oil drain plug the antifreeze will drain first before the oil.
If it does not bubble out of the recovery tank or geyser at all after 15 mins replace your stuck thermostat. for under $10
