Yes, still the same with the 20 seconds. It's very weird.


There has to be a leak in the system that is letting air in, because otherwise how is air getting into the system? All the signs of air in the system are there, and after I bled the air out, heat works again.

Scanning with an OBDII is not going to do anything because if the sensor is the problem, the ECU will not be able to tell. It's a Catch 22 in that sense.

Where is the heater core? I will check the hoses to see.

 

oh you'd definitely know if you've got a coolant leak in the cabin, it should smell sweet and your windows should fog up since the heater core is in the cabin., you should see two aluminum heater hoses change into rubber, and one should have a U-turn with a box following it.

 

very very doubtful that the heater core is leaking. It is metal(aluminum) out to where the hoses connect by the firewall in the engine bay. You might be getting hot heat when the heater is on but can still have air in it. The heat should get hot enough that putting your hand in front of the heater vent while the heater is on is almost unbearable with how hot it gets. The Most likely place to get a leak is the Radiator if it is an OEM with the plastic top and bottom or a hose. If you know someone that has a steep driveway, i mean steep, you could park it there but youll need to let the car cool enough to not have an "explosion" of antifreeze when you remove the radiator cap. I drove the car onto ramps, carefully as to not damage the front bumper, had to use 2x4s. THEN jack it up even more. You just need to get the front end up so that the top of the radiator is high enough that the trapped air goes foward. NOTE the aluminum line running across the firewall about 2 inches below the area where you windsheild wipers are, it is a line feeding the heater. You need to get the radiator cap above that, it will help significantly. Hope that helps

 

check you oil and make sure it is not "FOAMED" with the antifreeze. If the oil is good at least you know it is not getting into the oil. When the car is running is there steam coming from the exhaust, how about a sweet smell from the exhaust.. those are all signs of a blown head gasket. The steam would be coolant getting into a combustion chamber and exiting as exhaust

 

Are you sure that its not the a/c making you overheat. Maybe your condenser is very dirty. Just a thought..

Also you probably want to make sure its not a headgasket problem. Get your coolant tested with a cumbustion tester, just to rule it out.

 

You will see if there is a difference between dash and sensor = usefull.
And you can see actual values and how quickly they change / fluctuate = usefull.

In a sealed system it will suck coolant back in from the expansion tank when the cooling system cools down.
The pressure in the system it will also push out coolant into the expansion tank, with the rad cap being the "regulator".

So IMO the bottom line is: if you have a leak in a hose, radiator or heater core you're also loosing coolant.
No way around it.
There are no one-way leaks.

 

Heater + June + Florida =

 

It's not a headgasket problem, already checked for that.

The problem is that air is getting into the system when I turn the heat on. Also another symptom that is odd -- my overflow tank keeps filling up (I mean to the top, not to the fill line). I checked the cap and that is working fine, I don't know if it's part of the air bubbles in the system issue or not.

 

Ok that makes sense, I will have to pick up a scanner and test.

The system is pushing out coolant into the expansion tank, but it is not sucking coolant back when it cools down (so the expansion tank stays full until I pour it back into the radiator).

 

the system should only push excessive amounts of coolant into the overflow tank if the car is running hot. My overflow tank has NEVER changed levels.... Be sure that your fans are both functioning properly and like a previous post menioned .. the radiator and A/C condensor are not obstructed.. Bugs, leaves etc will cause blockage not allowing the cooling system to function properly.
Is the issue with the car getting hot only while sitting still or is it while the car is moving too?? If it an issue only while stationary there could be an airflow issue with a fan. Possible a fan is working but not working at capacity.