Either the cap is bad, your tank is either cracked at the seam or it has a pin hole that you can't see and the coolant is vaporizing ( steam ).
There are a couple of reasons why a 1996 Cadillac Seville SLS may overheat. The coolant may be low or the thermostat needs to be replaced.
There could be many reasons. Not enough coolant or bad flow, faulty thermostat, low oil. If the coolant freezes then it will overheat. If your car continues to overheat then you should have the coolant flushed and thermostat replaced.
could be your thermostat is stuck or perhaps and needs to be replaced.
Assuming it did not overheat before you replaced thermostat and water pump you may have installed the thermostat backwards. It is also possible the cooling system wasn't refilled properly and was air bound.
Does that mean that you replaced the thermostat AND the sensor? If not, you really need to replace the thermostat. A sticking thermostat can cause temperature swings and potentially overheat the engine. BTW, BMW engines tend to have serious problems when they overheat. Don't let it overheat or you might be buying a new engine.
Check your oil and see if it's milky. If it is then it's leaking inside. Does it steam out of the tailpipe? If it does you have a bad head or head gasket. have you replaced the thermostat? if you haven't, do that first, it may be stuck closed.
Even though you have already replaced the thermostat, there are other issues that can cause your Nissan Maxima to overheat. Your fan may be stuck and not operating as it should.
One reasons a Subaru Forester may overheat is because the radiator may need replaced. Another reason could be the thermostat.
because the water pump is not working properly....
Try replacing the thermostat.
The antifreeze level could be low, or the thermostat may need to be replaced, or the antifreeze line might need to be blead to get all the air out, the air in the line will make it overheat.
Have you replaced the heating core yet?