[angryBits]

Originally Posted by AZ_1LE

These engines are really sensitive to air pockets in the system, and it has a lot of places for air to get trapped. They basically put the system under vacuum before introducing coolant, and it is a lengthy process to get all of the air out. Wouldn't surprise me that that's all it is.

I 2nd this.

I haven't tried it, but I've seen some video about how you can burp it.
Might save some time.

[Artos]

If it were me, I would change the thermostat & bleed for air pockets simply to cover both as mentioned.