So I turn the motor off and I hear the heater hose going into the firewall bubbling... wtf? Air in the cooling system. Lots of it it seems. Is there a bleeder valve to which I can fill the cooling system with anti-freeze, run the car, and open up to run until I get just fluid?
Also how full should I leave the overflow tank?

 

The heater hose has coolant running through it. When you turn on the heater the blower blows the heat from that. I think.

 

I know that. My problem with it is that it sounds like a pot of boiling water which means it's not hot coolant flowing. There is enough room for the coolant to evaporate and bubble. It takes air to do that so the coolant lines are not under liquid pressure...

 

Sometimes one gets unwanted ambient air in the cooling system after engine repairs that opened a coolant circuit that allowed the air to enter. To cure it just wait until the engine is cool, remove rad cap and set it aside, start engine and wait while it warms up and burps air out thru the radiator neck. Add water as necessary to restore coolant level. Make sure that the heater is ON during this operation. Sometimes it helps to rock the car slightly to release trapped air. You might have to repeat a couple times.

 

That works... kinda what I was gonna do tomorrow morning before work. I just wish like my Honda and some other cars I've played with it had a bleeder valve that you could unscrew to push air out.

 

Sometimes heater cores leak (well, actually, they leak a lot). Other times the hose that goes to them leaks. When this happens they may or may not leak coolant into the interior, but they will let air into the cooling system, and no matter how much you bleed it just keeps coming back. Then you turn on the heat and your low coolant light goes on even though there is plenty of coolant and you think your motor is blown but it's not.

 

This is my vote,


You have a small leak that is letting the pressure blead off and causing the bubble.

 

No it holds pressure well... I ran the car with no radiator cap this morning and filled shaking the car with the heater running. Bubbles and gooey brown stuff started bubbling out of the top. All seems okay now.

 

Gooey brown stuff huh? Its time to flush and fill. Your coolant probably isn't working anymore, its just dirty water thats pushing dirt around in your engine.

 

I know. I'm putting my good radiator in this weekend which will involve a fill. The inside of the radiator looks pretty brassy green cruddy like.

 

It's easy and cheap to replace the radiator, so I've done all 4 of mine in the last 3 years. I also put in a plastic 5/8" tee from the $6 Prestone flushkit in the heater hose to simplify draining and flushing the cooling system.

 

Yea, I have a good radiator. Basically new. Pulled it out of my GSL when I took the motor out. New to that car by a few months. Gonna unbolt and swap it in this weekend. Since I'm going that route I'm going to do the lines to the oil cooler as well. Going to Mazda to get the washers and see if I can get the lines from them. If not I'm gonna overnight the lines from an auto parts store.