Why is my 98 cavalier getting hot when it has a new water pump, Heater core and thermastat plus, radiator has been cleaned?

sometimes you can get faulty thermostats, its happened before

It is quite possible that with the installation of the new thermostat and water pump, that your radiator cap is now failing. Ideally you always want to change it with the thermostat. In regards to the oil light. It should read pressure, not level, therefor the wrong weight oil under heavy acceleration, a clogged sensor or engine sludge can trip the oil light.

i agree with michael you should flush both the coolant system and oil system when doing a service as sludge will build up in both the sump and the bottom of the radiator worst case senareo is to change the radiator and to drop the sump off and clean it and the oil pick up pipe and filter

If it's just the coolant light that is coming on, check the level first. If the level is fine, smack the resevior a couple times. Could possible be a stuck level sensor.

there is an oil level sensor switch, i had one in my rivi. it is just on the side of the oil pan. it never worked well for me either. i just let it go. as long as the pressure sensor reads fine, u are good to go. happy motoring.