bubbles in antifreeze?

[AkronCrxSi]

I did a tune up on my buddy's car today and i took the radiator cap of to check the coolant and i noticed that it was bubbling up...i have never seen this before my guess it could be bad coolant maybe or a head gasket but im not sure...does anyone know what would cause this?

[Elegant Runaway]

last time my car bubbles in the coolant reservoir...it was a head gasket. or a pocket of air bubbles trap... burp the bubble?

[AkronCrxSi]

yeah i tried burping it so it must be the head gasket