ive got a 93 gmc 4x4 with a new goodwrench tbi long block crate motor with maybe 10,000mi if not less on it and it has been losing coolant and overheating out of the blue. now everything in the cooling system is new i mean EVERYTHING and it doesnt miss or steam or have milky oil like a head gasket but my hoses are hard and my overflow tank fills up way past the fill level but wont siphon back sometimes. now ive got alot of money and time in this thing and i cant figure out for the life of me whats wrong and i know this is a camaro forum but ive seen some good tbi info on here so any info would be appreciated thanks guys