2000 Chevrolet Truck

Engine Cooling problem
2000 Chevy Truck V8 Two Wheel Drive Automatic

I have a 2000 chevy c 2500 pickup series. About a month ago I did a major engine repair. Ever since then, the pickup has been working fine. Now the problem I am facing is that the engine is overheating. I replaced the water temperature sending unit thinking it could be the problem. But then I noticed that when I start the engine, it overheats really quick. I replaced the water pump, radiator cap, fan clutch, checked fan and fan belt, water thermostat and it is still overheating. I can feel the water return line that goes from the engine to the radiator bubbling and alot of pressure. I took the hose that connects to the water thermostat to see if it was stuck in the closed or open position but I couldn't tell. I put the thermostat back again and it continued overheating 240F. I decided to take out the water thermostat to see what happened and the temperature stays at 215 F. Please help me with this problem!
May 20, 2010.

Is that a 5.7 liter engine? Im guessing the major engine repair was a blown head gasket? Those are thin-wall casting cylinder heads, they crack very easily. If you have removed the t-stat with a new w/pump and fan clutch and it still overheats, I would lean towards a cracked head or bad head gasket. You can try chemical testing the cooling system for the prescence of exhaust gasses to see if it comes out positive.

May 21, 2010.