I have a 1991 2.2 that over heats thare is no water in oil and antifreez is not fomed i just replaced thermistat and i was wondering why it was over heating is it that thare is air in the system i still get air out once in a while

Did it ever over heat The intake manifolds on chevys can't take heat.
Cheak your antifreeze for oil in it look at your dip stick look for white fome.
If you see eighter of these condutions you need to fix the intake manifold fast or the engine will be shot.
It could be a valve problem to how many miles are on it .But check the oil and antifreeze

Try this How to Stop an Engine from Overheating

ignition timing off,check engine coolant level make sure coolant level is not too low.make sure you have 50/50 mixture of antifreeze and water in cooling system.if been long time i would flush out engine block and radiator.replace water pump and thermostat and replace radiator pressure cap.make sure front grille and radiator core not blocked restricted preventing air flow through the radiator.make sure cooling fans are working also.check engine oil if looks like milk shake you have blowed head gasket which will cause car over heat.

I would really be concerned about the antifreeze in oil, sounds like head gasket at least or head, block problem, even if you dont see antifreeze leaking, the engine can burn it and exit through tail pipe-white smoke or steam (beyond just cold start-up)

it sounds like the thermistat was instald back words. are thare is a air bubble thare try berping the sistem the hights heater hose if that dos not help check thermistat once in a blue moon thay do fail

If you've added two gallons of antifreeze, you need to find out where it's going. Make sure the antifreeze you are adding is diluted with water in a 50/50 solution. Pure antifreeze has little freeze protection and boils quickly. If there is no visible leak, check your oil for coolant contamination. Fill the radiator and leave the radiator cap off. Put the heater controls on hottest setting, but do not turn the heater on. Start the engine and watch the coolant. If the coolant level drops, add more to full. If the coolant is flowing thru the radiator when you first start the engine, the thermostat is stuck open and needs to be replaced. If the water is not flowing, then keep an eye on it and wait for the thermostat to open. Add antifreeze to keep the radiator full. Look for air bubbles or lots of foaming in the coolant. That would indicate a blown head gasket and the reason you are losing antifreeze. If there's no bubbles, and the coolant level stays full, put the radiator cap back on and see if the heater is working better.

get the gasket and the thermostat ... winter temp thermostat ... tho summer should be fine.... two bolts hold the housing on to the engine block... remove them .... clean off any of the old gasket... make sure you put the thermostat in the proper way... i believe the part that heats up goes toward the motor but check on that.... some do and some don't but i would apply some gasket goo and then bolt it back up. start it up.... check the level of the antifreeze and add if necessary... check for leaks..... put the rad cap back on after it's heated enough that water is flowing.... as it builds up pressure ... check for leaks again.... i've left this for last but it should be first.... drain some of the antifreeze before you start the job.... doesn't have to be all of it.

after a few cycles of heating up... check that the bolts are still tight and that there are no leaks... remember one thing... antifreeze will leak where water wouldn't.

Robert

definately a head job !!

Your thermostat is probably stuffed and not opening you can do without it if you so choose to or you can replace it. It is located in you water pump houseing and you will need to replace the seals(gaskets) if you open it up but I would be checking that first if you have no obvious leaks.