If you're driving and this happens, immediately crank your rad bleed screw a little. If a lot of air hisses out before coolant, then you likely have a bad fire ring. You can confirm with a block test kit to check for combustion gas in coolant. Sadly I encountered this and an currently rebuilding my engine.

Andrew

On Sun, Jul 7, 2024, at 4:52 PM, John Rodgers wrote:
> When the pressure cap blows off the coolant tank and coolant is lost, sure
> sign of blown gasket, Right? 2.1 L