I having an issue with air bubbles that won't stop coming out of the radiator. I recently did a swap and have not driven the car. I hooked up a new Mishimoto radiator and burped it from cold to when the thermostat opened up - the heat **** was also set to hot.The problem is when the thermostat opens up I get a constant bubbling of air being released from the radiator. Not a crazy amount of bubbles, but maybe four bubbles at a time with a two second pause. Again only happening during when the thermostat is open. I checked for a head gasket leak by doing a compression test, 225, 220, 220, 230 and a block test that came out negative - tried three times. I changed my thermostat and thermo-switch (fan wasn't turning on) as well. I'm all out of ideas.

Let say there is no head gasket leak, what would be another way of air getting into the system? Since this a pressure system, I can't think of any other way of air entering.

 

Do the process again but use one of those spill proof coolant funnels made for the car, this allows the coolant to be past the lip of the radiator and if you still get bubbles after 3 cycles of the fan then the head gasket is bad or you have a cracked head/block.

 

When you're not using a funnel, after the engine warms up to a certain point the radiator is going to naturally overflow due to expansion. Put the cap on at that time and make sure there is coolant in the expansion tank. There should be warm / hot air from the heater at this point. Test drive until fully warmed up and make sure the heater keeps working. Then park level or facing uphill and wait until completely cold and check in the radiator. If it is not full to the top, repeat the process.

 

It was blown head gasket.

 

That's unfortunate