I get what sounds like bubbles in my heater core only when I set the temperature in the center. If I turn it to any level of heat, no sound. If I set it all the way cold, no sound. In between center and about halfway through the blue marks, it'll bubble.

I did recently replace my heater core hose, and a couple weeks later had to deal with an air pocket in the cooling system because I didn't bleed it correctly. But I should be good now. Any ideas?

 

I heard bubbling noises were normal.as long as there are no leaks, no unusual smoke out the exhaust and temps are within normal specs, there is nothing to worry about.

 

 

The best way to bleed the coolant is with a Lisle funnel.

Here is a link:

 

Had a similar issue with a friends car and used a similar method as Torque Restorations. Came out fine after.