Where is the thermostat located ? I'm looking for the two bleed valves.

the drain valve should be below the transmission lines side on the bottom or near the bottom

check your vacuum actuated heater valve assembly under the hood for proper function .possible malfunctioning thermostat

What engine 2.2 or 2.4 ?
Important: On vehicles equipped with the 2.4L engine, open the coolant air bleed valve. The coolant air bleed valve is located on the top of the thermostat bypass pipe/heater pipe assembly. Close the valve once a continuous stream of coolant is expelled from the valve.
Does the cooling fan come on ?
Notice: When adding coolant, it is important that you use GM Goodwrench DEX-COOL™ coolant. If coolant other than DEX-COOL™ is added to the system, the engine coolant will require change sooner: at 50 000 km (30,000 miles) or 24 months.
Close the radiator drain ****. Remove the drain hose.
If previously removed, install the engine block drain plugs.
When installing the drain plugs, use pipe sealer GM P/N 12346004.
Important: On vehicles equipped with the 2.4L engine, open the coolant air bleed valve. The coolant air bleed valve is located on the top of the thermostat bypass pipe/heater pipe assembly. Close the valve once a continuous stream of coolant is expelled from the valve.
Fill the surge tank to the base of the filler neck.
Start the engine with the pressure cap off. Let the engine run until the upper radiator hose starts to get hot.
If the coolant level in the surge tank is low, add the proper mix of coolant until the level reaches the full cold line.
Important: After servicing the cooling system, and if the vehicle is equipped with an intermittent low coolant light, an occasional low coolant light may be encountered during some extreme driving maneuvers. This complaint should be eliminated by removing the surge tank cap and adding coolant to a level just at or above the full cold line when the system is cold.
Install the cap onto the tank with hand tight pressure.

Those valves sound like fuel pressure test ports. Press down the center of valve and see if gas comes out. If it does, those valves are on the fuel rail, not in the coolant system.
A bleed valve is a bit different. Looks kind of like a grease zerk, with a small hole on its little round head. You put a small wrench on the valve and turn it as if loosening it, but only a turn or two to open it and let coolant or air out the hole on the valve. Look for it on or just close to the thermostat housing.
If you have no bleed valve, best practice is to fill radiator and overflow tank, then start car with the radiator cap off, and let engine run until the thermostat opens (upper radiator hose will get hot when thermostat opens). Now turn off engine and replace radiator cap. This usually gets all the air from coolant system, but sometimes you have to do it again.

look at your top radiator hose is there a small bleed valve at the top of the thermostat housing when the upper hose attaches to? If so loosen the bleed valve and allow the cooling system to purge the air out of the system you can tell when the air is out of the system when a steady stream of coolant starts to flow out of the bleed valve, if there is no bleed valve take the top radiator hose off of the engine side and allow the cooling system to purge the air out through the top of the engine that way

Was the thermostat changed? I would suggest replacing the thermostat refill the system with new coolant and purge the air out of the system.

Fig. Thermostat and housing-2.0L

Fig. Thermostat assembly-2.4L engine

Fig. Air bleed valve (1) and thermostat housing (2) 2.7L-engine


Hope helps (remember to rate this).

3.2L & 3.5L Engines

1. Before servicing the vehicle, refer to the Precautions section.
2. Drain the cooling system.
   WARNING Do not use pliers to open the plastic drain.
   
3. Remove or disconnect the following:
   NOTE It is good practice to turn the crankshaft until the No. 1 cylinder is at Top Dead Center (TDC) of its compression stroke (firing position).
   Negative battery cable Coolant recovery cap and open the thermostat bleed valve Drive belts Timing belt Water pump mounting bolts, noting the position of the longer bolt Water pump. Discard the O-ring seal.
4. Clean the gasket sealing surfaces, being careful not to scratch the aluminum surfaces.
   
   
   Fig. Water pump bolt locations, make sure to note the position of the longer bolt
   

To install:

1. Install or connect the following:
   WARNING Rotate the pump and check for freedom of movement.
   New O-ring and wet with clean coolant prior to installation. Be sure to keep the new O-ring free of any oil or grease. Water pump with a new O-ring. Torque the water pump-to-engine bolts to 105 inch lbs. (12 Nm). Timing belt Drive belts
2. Fill the cooling system by performing the following procedure:
   1. Close the radiator drain.
      
   2. Open the thermostat bleed valve. Install a 1 / 4 in. (6mm) clear hose about 48 in. (1.2m) long to the end of the bleed valve and the other end into a clean container. The intent is to keep coolant off of the drive belt(s).
   3. Slowly, refill the coolant recovery bottle until a steady stream of coolant flows out of the thermostat bleed valve. Gently squeeze the upper radiator hose until all of the air is removed from the system.
   4. Close the bleed valve and continue to fill the coolant recovery bottle to the proper level. Install the cap on the bottle and remove the hose from the bleed valve.
3. Reconnect the negative battery cable. Start the engine and allow it to reach normal operating temperatures.
4. Check the cooling system for leaks and correct coolant level.
   WARNING Be sure that the thermostat bleed valve is closed once the cooling system has been bled of any trapped air.

Good luck (remember rated this).

No bleed valve. If you want to get the air out of the system, just run the car until it's hot and the thermostat opens, and then run it some more so that the coolant is fully distributed. The air will get to the top of the engine - the filler cap. Then after it's cool you can refill the engine, and the overfill tank.