Air trapped in ICE coolant system

Thermostats sticking closed haven't been anything like common in my own experience, anyway.

They are opened by the force of expansion of a solid wax pellet. Trying to make that not happen would be like answering the old "what happens when an immovable object meets an irresistible force?" question.

The only way I know of to create a won't-open situation is an earlier severe overheat, so severe that the wax pellet blew its cylinder apart. Then the thermostat is well and truly dead and will cause repeat overheating, even if it wasn't the reason at first. Thus the usual recommendation to change it in an engine that has badly overheated for any reason.

In the other direction, they're just closed by a spring, so a bit of rust and stickiness might be enough to stop one from closing completely.

 

Did you NEED to machine the head? Did you check to see if it was warped?
The machine shop would probably check it for you for no cost. You just need a KNOWN straight straight edge.

Unless you completely flushed the WHOLE coolant system, you may have left over exhaust in the coolant.
The text may not be accurate. Putting a pressure tester on the coolant system and checking through the
spark plug holes for coolant leaking into the cylinders would be a better test. And/or a leak down test.

 

There is an air release valve in the back of the engine, you can open it and let air out from there.

Just zoom in on my picture to follow the tube to where that valve is.

 

These are a couple better pictures so you can see it easier.

 

Not every Gen 3 has that valve. My 2010 happens to have it. Lots of Gen 3s from later years don't.

I used to think it was a model-year thing, but they cross the same part number to all years of Gen 3. So it was just a production change at some point.

But never fear, whether your Gen 3 has that valve or not, all Gen 3s have the degas-bottle style of cooling system. It's built with special extra hoses (the ones shown here in blue) that collect air from high spots in the system and deliver it to the top of the degas bottle where it belongs.

 

Has classic blown head gasket symptoms. Something got missed or head warped bad.

Was there some excitement there at the end before you went after that gasket a bad overheat?

G3 engines are a nightmare.

 

It is most likely not that you are having any trouble burping the air out of the cooling system.

It sounds more like the engine is just inserting exhaust gas into the cooling system every time you run it.

 

If I'm Capt. Obvious here, apologies in advance.
At very least, after doing the head, there should be a better understanding of the EGR system and one less headache to worry about, if there is a next time with something as confusing - and there is no techstream around to hookup.

 

One thing I learned from my past experience is that any aluminum head/block need to be machined when replacing head gasket, especially if the head gasket was blown and/or the engine has been overheated. Those aluminum things get easily warped even with normal use.

 

Zz engines .. . Look really deep inside . You'll probably replace .

 

Maybe check them with a straight edge though, verify the need?