Air lock in coolant system

I agree with your logic. Attached vid addresses bleeding. Sounds like at low rpms, not enough flow to transfer the heat. So bubble or maybe a partially obstructed core. There are a couple of vids on clearing a core... GOod luck, let us know if you figure it out.

For car running hot and overheating issues, I suggest to you go through this help links. Click this link below and go through the troubleshooting procedure to take care of the problems: ----Car runs hot? http://howtobyme.blogspot.com/2011/11/car-runs-hot-in-traffic.html
-----------All types of car overheating problems and troubleshooting?

http://technoanswers.blogspot.com/2011/11/all-types-of-car-overheating-problems.html
Car freeze overnight and started overheating while driving?http://technoanswers.blogspot.com/2012/01/car-freeze-overnight-and-started.html-----------Engine Overheats and heater blowing cold?

http://howtobyme.blogspot.com/2011/11/engine-overheats-and-heater-blowing.html

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Car overheats and Air blows hot at idle?
http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html
--------overheating? http://schematicsdiagram.blogspot.com/2011/12/buick-century-overheating.html
----------Car engine Overheats and transmission starts slipping?http://schematicsdiagram.blogspot.com/2011/12/car-engine-overheats-and-transmission.html
----------This details will help.Thanks.

This is usually caused by an upside down thermostat, or the system has a lot of air in it. CHECK the radiator cap, if the cap is bad, you often don't pull coolant from the reservoir back in to the radiator as it cools off, instead it pulls in air. The air causes pockets of air to collect in the engine causing overheating and sometimes the air gets in to the pump which causes what we call "Airlock" the pump simply cant pump air so it ceases to pump at all. When that happens, sometimes hitting the brakes hard will get it to pump again. That is an airlocked pump.
Caps are cheap, replace it, and be sure that the reservoir is between the full hot and full cold lines at all times.
If it starts blowing off coolant, you could also have a cracked head or head gasket. The cap is a simple thing to try first, you have to have a completely full system, no air!

REPLACE THERMOSTAT.MAKE SURE COOLANT SUPPLY PIPE OR COOLANT RETURN PIPE NOT STOPPED UP AND YOU HAVE ENOUGH COOLANT IN THE SYSTEM.REPLACE THERMOSTAT.CRANK ENGINE UP AND LET IDLE UNTIL WARM UP KEEP EYES ON TEMPERATURE GAUGE. WHEN ENGINE THERMOSTAT OPEN COOLANT HOSE SHOULD BE HOT.IF NOT TURN OFF ENGINE.USE LARGE RAG WAIT A WHILE BEFORE REMOVING RADIATOR CAP CHECK TO SEE IF COOLANT LEVEL DROPPING IF SO ADD MORE COOLANT.CRANK ENGINE UP UNTIL THERMOSTAT OPENS UP.HOSE WILL GET HOT.IF STILL COLD CHECK COOLANT LEVEL.ONCE YOU AIR OUT COOLANT SYSTEM RADIATOR HOSES WILL GET HOT SO YOU WILL GET HEAT.IF COOLANT LOW YOU WONT GET NO HEAT.

May just be low coolant level. Remove rad cap, or if none, coolant return bottle cap, and start engine and run heater while doing this. Now pay attention to coolant level and add as needed to top up the system. Let it run with cap off until rad fan comes on and off, 2 or 3 times and keep adding coolant if level goes down. Keep an eye on temperature gauge while doing this. It almost sounds like your coolant got low, or is low, and your heater has an airlock. Once coolant circulates back through heater and level is correct, see what happens.

have the cooling system checked for exhaust, its called a block test, also have thermostat checked and make sure coolant is full.

hello , sounds like an air lock in coolant system , drain system and re fill very very slowly , if you think you are filling it slowly enough slow it down even more , also replace thermostat to ensure its opening and closing properly , hope this helps

I think you could be right about there being air trapped in the system.
Or the heater core(radiator) is plugged.
Either way you need a pressurized radiator coolant pump to put the coolant in without air being trapped.
Although,i have seen it done by jacking the vehicle up high enough that the radiator was now higher than the heater core level, and then the coolant was put in.
But this is dangerous to try.

Be sure to have heater (not defrost) on when refilling rad with coolant, and leave cap off until rad fan has come on & off 2 or 3 times, then replace cap. Airlocks are common on vehicles cooling systems, and will cause symptoms you are describing.

Let your engine warm up with the rad. cap off and see if the coolant level drops. and make sure your overflow is full. It blows cold air because there is no water getting to the heater core. And it shows a normal(ish) temp because the water needs to be touching the temp. sensor. I really do think there is air in the system and there is not enough coolant but hard to tell from here. Also as with overheating any time make sure to check your oil and look for any coolant as the head gasket seldomly holds together if the motor overheats.