Hey guys,

I recently heard some air bubbles in my cooling system during startup (cold). I haven't done any coolant changes or removal of any cooling pipes. How can air bubbles get into the cooling system then? I did upgraded my rad and thermostat a year back but it was running fine all year long after my mechanic bleed out all the trapped air.

I do have a cracked evap hose (waiting for dealer to replace) but will that suck in air to the system?

I'm worried it's my head gasket...

any ideas? Thanks!