Originally Posted by Lauren3265

Hello, I just bought a '97 Z28 on January 30th (last week). The seller said all it needed was a new water pump...so the next day, I bought a new water pump, battery, thermostat, and antifreeze.
We removed the old water pump and old thermostat and replaced them with brand new ones and well as used the antifreeze. I went and ran a test drive, and almost immediately it began to overheat and smoke from the mufflers and underneath the hood, and the thermostat was removed. When I got home (let me mention I am working with another person who knows a lot more about cars and is making the decisions and such) I...we...used a sealant to fix the head gasket and warp heads. After running the car as the directions said to, massive pressure built up underneath the radiator, and the cap blew off and liquid shot out. The car then began to shut down. The next day, we used the bleeder valve to bleed it, and it ran about 5-10 miles perfectly, and then it began to overheat again. There is also no heat from the heater.

Originally Posted by Camaro 69

Need you to clear up a contradiction, did you ever have the new thermostat in place? No thermostat can be a cause of overheating since the radiator can't then do it's job. Are your cooling fans going on? I see no mention, and if they aren't turning on, your engine WILL overheat. An overheating engine builds up a lot more pressure, and that could be the only reason the radiator cap blew off. You'll be lucky if that's the only thing that did blow from overheating. You also really need to make sure that the cooling system is bled well of all air, or it can cause overheating problems. Did the engine act like this when you test drove it before buying the car? Because you mention it overheating and smoking right after replacing the pump, and something that obvious would have been noticed before you bought the car.