2004 cobalt makes a gurgling sound (like drinking out of a straw when the glass is down to the ice) until the engine is warmed up to normal operating temp. Coolant level is OK. What do you htink it is?

from what you describe either a bad radiator cap, or a leak in the small hose going to the resovoir,or the line within the resovoir tank is to short or missing,this is whats happening,engine warms up to a point that the cooling system is building pressure,the radiator cap has a set presure release to it you might see the figure direcly on top of the radiator cap, 12-14 lbs rated. it usualy will read something like that, so as that warming engine builds pressure in the cooling system it will eventualy surpass the rating of the radiator cap ,and out it goes and flows in that small line to the overflow resovoir. now when the engine cools back down it now will create a vaccum and should draw that water back from the resovoir to the radiator,but if the hose or hardline that is usualy integral within the resovoir is bad cracked or missing, it would be the same as trying to drink a soda through a straw,but the straw is not inserted below the surface of liquid.or if the straw was cracked, no fluid can be vaccumed up through the straw, the resovoir works on that same principle, it must have a good unobstructed line from radiator to the resovoir,and the line inside the resovoir should go nearly to the bottom of the tank, so the water can be vaccume syphoned out just as drinking a soda with a straw.so check to be sure the line is all good no obstructions,no cracks, and that there is a line that continues within the resovoir tank almost to the bottom as well and it is in good shape as well. last check that radiator cap to make sure the rubber as well the upper gasket portion are still there and not cracked/dryrotted. if all that is in good working order then your radiator should be able to recover the water back.just like sippin a soda through a good straw

Sounds like a faulty temp guage/r a strange malfuntion in a sensor to me as well, only doing it when it going up hill really makes no sense for the way the cooling system works so I doubt that its actually running hot, which is likely why he asked about the gurgling noise, it would force water back into the resivoir if it was running hot assuming that the thermostatic radiator cap is working properly.

if this car is on the cold start injector when it is defective. Injects additional fuel to the engine is still warm. Is it to feel warm by running more than normal gasoline smell?

It is possible that your thermostat is stuck open. Normally, the thermostat remains closed when starting cold, confining coolant to the engine block and cylinder head until it heats up. Once the coolant in the block is warm (usually within 10 minutes), the thermostat begins to open and let coolant flow into the radiator to cool it down some. A properly operating thermostat will continue to cycle until the coolant reaches the operating temperature of the thermostat--usually around 180 deg F. Then the thermostat will continue to adjust its opening to maintain that temp.

Thermostats can get stuck in both closed and open positions. When stuck closed, the engine will quickly overheat. When stuck open, the engine will take forever to warm up--especially in cold weather because the coolant is continually pushed into the radiator and cooled off before it ever has a chance to get warm. Changing the inexpensive thermostat may help correct your condition.

Staqr by making sure the coolant level is full in the radiator. When the engine is cold remove the radiator cap. If you can't see coolant in the radiator you'll need to add some. once it is full replace the cap and start the engine. Do you have heat now?

If not is the check engine light on?

Do you have a temperature gauge? is it reading lower than normal? The needle should be around the middle mark. If its near the quarter mark than you could have a thermostat stuck open which would cause the check engine light to come on and store a code for coolant temp below operating temperature. I think its code P0128.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

All you need to do is fill resivior and radiator, if theres no cap on radiator then fill resivior and then start and let reach operating temp, leave cap off while topping off as engine warms replace cap and run until fans run then shut engine down and let cool after cooling remove cap start engine and add if needed, hope this helps.

Air pocket need the thermostat housing.

Air is not a good conductor of heat.

Park you car on a hill and let the air pocket to work itself out to the cooling system.

A shop will charge $65+ to purge the air out.

The "check engine" warning light advises that the vehicle is in "fail safe" mode. That means only some of the car's capabilities are operational, just enough to get you to the nearest service point. You probably should not drive it any further than that. Have your service man download and analize the fault codes from the ECM which will indicate what the problem is.

Sounds like either your thermostat is bad and needs replacement, or you have air in the system. Since bleeding the system is free, start there.
When the engine is cold, open the radiator cap and start the engine. Turn the heater to full hot and turn the fan on as well. As the engine warms up, the water in the radiator should start to gurgle and decrease if there is air in the system. Keep filling it as the engine reaches normal operating temperature. When it does, it will start to spit coolant back out. Cap the radiator and you should be ok.
If that was not the problem, then the thermostat is your next best bet. Replace it with a factory OEM thermostat and bleed the system using the aforementioned technique.

Hope this helps,
matthew

Helicoils will not harm the balancer. So, forget that. First, I recommend that you determine true top dead center by placing a drinking straw into the #1 plug hole and turning the engine by hand till the straw is at the top of the piston stroke, then back off a short distance, remove the straw, and insert a bolt several inches long, the exact thread size and diameter as the ones on the sparkplug, down into the plug hole, far enough so that it contacts the piston, then back off a bit (using fingers only) then, turn the engine slowly by hand till the piston again contacts the bolt. Use a crayon and make a mark on the balancer using 0 on the timing tab as a reference point. Spray some paint on the exposed bolt threads so it can be re-installed at the exact same depth again. Remove the bolt and turn the engine backwards by hand and again insert the straw. when it nears TDC again, put the bolt back in, using the paint on the threads as a guide as when to stop, and continue turning the engine till the piston again rests against the bolt. Make another reference mark as you did before. The two marks will be about an inch or so apart. Exactly half way between those marks is true TDC. If it is anywhere other than where the factory mark is, use a hacksaw to cut a permanent line into the balancer and use white paint to mark it. You can now time the engine using the new mark as an exact reference.
I actually have made a tool for this by breaking off the ground strap and electrode also removing the entire porcelan top as well, from an old spark plug and tapping a screw thread into the empty shell, then placing a bolt into the shell rounding off the top so it is less likely to mark the piston top. Never turn the engine by any means besides normal hand/wench method and never force anything. The entire operation actually takes longer to write than it does to do.