My 93 K1500 started burning antifreeze and leaking antifreeze and oil yesterday. I was driving home and going up a hill when the truck started to rev high at around 45mph and wouldn't shift. Then it overheated and died out. I thought it was the thermostat so I switched that and drove it the rest of the 5 miles to my house. When I started it next time it was blowing white smoke everywhere and over heated within a few blocks of my house. It is leaking antifreeze and oil out of the passenger side of the engine. My dad said either it's a bad head gasket or a cracked head/block. Which one of these is it most likely. I hope it's not a cracked block/head because I just put this used motor in 2 weeks ago. :banghead:

Sounds like it was probably the head gasket to begin with, but there's no telling what other damage you did by driving it. How long did you drive it after it overheated? I used to have an 87 4.3L that I ran into the ground... it had one of everything blown. It'd overheat, but never died...

Get under the hood and see where the oil/coolant is coming from. If you had a shop do the engine, take it back to them and demand a new engine.

oops... just saw "used motor" in the original post... not really much to do there.

i took the whole motor apart. The leak is on the passenger side and cyllinders 4 and 6 were filled with antifreeeze. I'm going to replace the head gasket and see what happens

Check the heads and deck with a straightedge before assembly. Overheating may have caused them to warp slightly.

could have but i doubt it because I shut it off as soon as it started to overheat