on my 96 oldsmobile ciera 3.1 v6 i bought a new napa # 222 thermostat and installed it now it seems when i start it cold i get no heat sometimes and my temp gauge swings up to 3/4 semi fast then after some time it comes back down and then a few minutes later i get heat then sometimes the heat turns cold and the gauge starts going up again after running for over 25 minutes everything is good. the system is bled correctly could the brand new napa thermostat be bad? I changed the thermostat because the original was stuck open, i also replaced the water pump because it was starting to leak and there is a new radiator cap also.