No, not since I burped it...

 

Same old story's lol I had this a few times have u bled it properly with my alloy rad I had to bleed it near the throttle body but I completely flushed everything thru at the block also. Us be a tiny hole in return pipe hence pushing water into overflow n not returning bk when cooling if not that it's the seals do u get bubbles cold start sum bubbles when hot is normal it's agitation from water pump unless it's gushing lol

 

this happened to me, it ended up just being the conection hose between the two tanks so have a good look in and around there