[Joe's Garage]

That way, when you run the engine, any air will bleed of fairly quickly.

There should not be ANY bubbles circulating in the system when the water is full and it is at operating temperature. None.

Any bubbles, particularly a steady stream of little tiny bubbles indicate a leaking gasket. Not blown, just leaking.

I think your spark plug for #5 looks a little too clean compared to the others. That would be where I would look first.

Good luck!

[alanmay0]

would this cause the engine temp to go up to and past 250 degrees

[prostreet64]

you bet, super heated exhaust gas will heat up the coolant very fast, of course depending on how compromised the gasket turns out to be.

[Joe's Garage]

We had a 'leaker' that would fluctuate between 230 and 250* steadily up and down. Never overheated, just ran hot and fluctuated.

And there was always a steady stream of tiny bubbles in the coolant.

Gasoline's ignition/burn temp is 495*, and the temp inside the combustion chamber, with the gases burning under pressure, is around 2800* and can approach 4000* under certain circumstances.

So, YES, even a small amount of combustion gas will heat the coolant up really quickly.