okay so i purchased another 94 sierra 4x4 yesterday. i got it to replace the tranny and t case on my black sierra. but for now im driving it. the guy said the heads were cracked. well actually the motor runs great, but the second i put a thermostat in it pressures up and overheats right away and its a brand new thermostat. so theres no thermostat in it right now. i can put around town if im not goin to far. the head gaskets not blown the oils clean i checked. heads are good head gaskets good. not leaking any water. but the oil pump needs to be replaced its got low oil pressure but i dont think thats the issue. if anyone may no what could be up. let me know thanks guys
