I have a 1990 Chevy Silverado 350 TBI. I was driving home and my engine overheated. I pulled to the side and started seeing steam coming from the radiator. I thought my thermostat must have gone bad. I changed the thermostat and heater core, as my heat went out a couple of weeks ago. I started it back up, and water was leaking from my radiator. So I replaced my radiator and started it back up, topped off the water, drove it around and my temperature gauge was going crazy. It would jump from 160 to 260. I would gun it and the temp would start dropping back down to 195. As time went on it would jump back up and drop back down. no consistency. My water pump is not leaking or making noise, nor any water coming out of the weep hole, does anyone have any knowledge as to what this might be????????
TIA