986 popping sound from car. when hot.
 

Hi Folks

I have a 986 2.5l. and when it gets hot I am getting this popping spitting sound coming from right behind the drivers side. I thought it might be air in the cooling system. Tried opening the bleeder valve. Even replaced the bleeder valve.

Car has never ran out of coolant.
No coolant in oil
No sign of leaks

When this happens there is no change in engine performance, revs and drives fine.

Might be unrelated but I can only get warm air from heater when I set to Hi, it remains cold at all setting up to the highest (HI) then its roasting hot...

Any ideas?