1993 Park/AVE Over heating problem.

I just replace the water pump on my P/A . Now it overheats way over 200 degrees. This did not happen before I change the pump. The pump started leaking and I would see the temp. fluctuate between 190-200 degrees. Now it overheats to 250 or more. Core heater hose feel warm, top radiator hose is warm, lower pump radiator hose is cool (cold). I'm going to change the thermostat today and see what happens. Any other ideas are appreciated? I changed the thermostat and flush the radiator. I have heat now and the temp is holding at 190-200, but now I have smoke coming from around part of the exhaust manifold. Could this be a head gasket leaking? Thanks

Thats what it sound like. I there any water on your dipstick or does the oil look weird in any way? My buddy blew one on his GN and his oil looked like a melted cocolate milkshake

well, hypsi is right. when you changed the water pump, you may have accidentally let a piece of dirt into the cooling lines, and jameed the thermostat shut.