My 94 ciera is running hot. I filled the overflow, but can't get the rad. cap open or figure out where to fill the rad., or check the level. The drain to the overflow is blowing small air bubbles into the overflow. Before replace something I just want to make sure the coolant system is full.

engine cooling not A/C cooling of humans...
fill it slowly at rad.
with the hightest hose removed at one end.
not put it back. (hose)
repeat with rad cap off. filling,,, AF. (antifreeze is AF)
get the rad full of 50% AF
cap off, start engine and stop it when the coolant starts to overflow.
if the coolant drops add some now. running.
if it overfills. good, that normal (hot AF expands pure physics)
then cap the rad.
drive around block.
come back park .
let it cool, and check cap level at rad neck
add AF to fill
then drive around block again. and check cold again.
is it now stable, its ready to rock. (drive)
if it is not , there is a problem.

if now good, put the correct level in side overfill tank.
make sure all hoses there are good.

this is an art form , no engine stated, here, just Rodeo
there are 4 engine here, in uSA. for one car.

but my answer above covers most engines.
but there are some exceptions on some...
the thermostat must have the bleed (jiggle pin,etc) on the up hill side. on all engines. or it will be hard to bleed.

just dont drive a long ways until, the cold rad proves (cap off)
that it is really full.
then get the side tank working, with the hoses good so it
can suck back AF when cold, or it will drop each day. driven.

Make sure all the drains are closed, start filling the rad and allow the coolant time to drain down, then fill again. Keep filling the rad unit it no longer drains down, just make sure to stop filling it when the level in the rad is just barely visible when looking down inside it. Now fill the overflow bottle to the lowest level mark. Start the car and turn you heater on to full heat. Let it warm up to proper temp, may/may not need to put more in rad. Keep an eye on the level in the rad it will expand and may overflow, if it looks like it will overflow use yout tester to remove some fluid. Once you see the coolant flowing throug the rad wait a few minutes, then put the rad cap on. Let it run a few more minutes to get the rest of the air out, then drive like normal. Check the fluid level in the overflow bottle (engine cold) over the next few days fill to proper level as needed.

If you dont have an external coolant leak anywhere under your hood that has shown up on your driveway it could be the intake manifold or the headgasket leaking. Also check the thermostate to solve the heat issue.

take off the radiator cap and fill the rad with antifreeze. start the montor and keep watching the level of the antifreeze and keep adding as necessary. when the termostat opens you sould shee a sudden drop in level.... keep adding antifreeze. squeezing the upper rad hose will help remove air bubbles. BE EXTREMELY CARE OF THE FAN AND OTHER MOVING PARTS TO PREVENT INJURY. after you are satisfied that you have added enough fluid put the rad cap back on. fill the overflow tank to the leven it indicates.... take it for a drive and let it cool down. open the rad cap and top of the fluid if necessay.

You could just be burning it up. Do you have accesive white smoky exhaust?
Have you filled radiator completely. Fill completely once while vehicle is running, burp upper radiator hose while adding. Then wait 10 minutes and the coolant level should drop in radiator as it will flow into engine block. This is where you want to fill the system again, and put the cap on.

probrally the thermostat or water pump

Run engine from cool, with rad cap off & heater on heat (not AC) and watch for circulation through rad when engine reaches normal operating temperature. Rev engine slightly from time to time for a couple of seconds, to increase flow & help bleed air out of system. Let it run for a while, and watch for increased flow in rad 2 or 3 times. Probably see air bubbles at same time.Hot coolant from engine comes in top, and back out bottom to engine after cooling in rad. The increased flow in rad ,indicates thermostat is opening & circulating cooler liquid back into engine. After 2 or 3 times put cap back on & fill return bottle only to line specified as warm/hot engine level.

Start with engine cool. Remove rad cap, top up coolant, start engine, & turn on heater (not defrost). let it run until up to normal operating temperature & radiator fan comes on, then shuts off. Let it do this about 3 times before you put rad cap back on & top up return bottle to proper level. Every once in a while, rev engine slightly for a few seconds while your doing it, to speed up bleed by increasing flow. Keep an eye on temperature gauge for too hot, and fan not coming on, if so, shut it off.

Generaly 2 possabilities, low coolant level or cloged heater core/hoses. Check low coolant first as this is thew easiest and usually the simplest solution. With the engine cold, remove the rad cap and overflow cap. Fill the rad full and the overflow to the cold level and replace the rad cap and overflow cap. Start and warm up the engine. If you still do not have any heat, then let the engine cool and drain the rad. Remove the heater lines and try to bolw air through them (if cloged, then replace them). If the heater lines are clear, then blow air through the heater core intake and see if you get a good flow out from the heater core, if no, replace heater core.