04 Grand am Cooling system issue

Good Morning

I have a 04 six cylinder grand am with 150,000 miles. It has a weird overheating problem. We have replaced the thermostat, and the water pump. When we put the coolant back we used a tool to pull the antifreeze back into the system. Until it gets to full running temperature. It will overheat slightly, when it over heats it pushes coolant out the overflow tube. Once it is at full running temp. It quits overheating, but if it is idling it has not heat. Once it is running down the road or the accelerator is pushed to bring the RMPs up it gives heat again. This all started after there was a broken wire to the started that made it seem like it need a new alternator. I don’t know if this is a coincidence or not. Any ideas on what could be the problem.

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I assume it all worked fine before replacing the parts mentioned, and the problem appeared immediately afterwards. If so, there’s most likely an air pocket in the cooling system.

Exactly what tool was used to refill the system? Was the person who did the work experienced in using this tool? I suspect the root of the problem lies in the tool or its use.

My info indicates that this system uses a surge tank. Remove the pressure cap ONLY WHEN THE ENGINE IS COLD and inspect the coolant level. Also open the coolant bleed screws and see if air comes out rather than liquid. If necessary, add coolant up to surge tank with the bleed screws open. Shut the screws when liquid comes out, then top up to the “full” mark in the tank. There’s a good chance that will take care of it.

I agree with Gary T about air in the system.

Another slight possibility is that the thermostat was installed backwards. But the symptoms match an air bubble in the cooling system better.

Check to see if the radiator cap is the highest point in the cooling system. If not, jack up the front of the car enough to make it the highest point and run the car for a few while adding more coolant if necessary. Leave the cap open while running the jacked up car.