I have an 86 Aries with only 38.000 miles,when i bought it about 6 months ago It had 32.000 miles,the original motor blew up at 36.000 miles,i put in a good motor with 84.000 miles,and everything was fine till today,It will not hold coolant,and It Is going somewhere,not out the exhaust,the oil looks good(nothing milky)
and nothing on the driveway,but everytime i drive it now the temp guage goes up to the max,then comes down,i replaces the thermostat,and coolant temp switch again,but after It cools down,the radiator Is 1/2 empty,and the overflow Is only 1/2 full,but i see bubbles in the overflow after about 15 minutes of idling.

any ideas?