Losing a noticable amount of coolant everytime I drive. Have to fill up the overflow bottle from min to max about every 3-5 days of driving. Very noticable white smoke (outside temp in the 30s) coming from the tailpipe on start and for the first5 min of driving. Smoke stops until I park and it sits for a couple of hours and it does it again. I can't find any leaks under the hood nor are there any puddles of coolant under the car after it sits.The oil looks goodat the dipstick andcap with no noticable contamination. I ran the car withthe radiator cap open andwhen itwas warm. It started a very slight overfow but no bubbles.The engine hasnever overheated (in the past two years that I owned it anyway and the problem started about a month ago). The Mazda Specialist repair shop noticedthe coolant wasa "little low" when it was in for a failedcamber angle sensor a few months ago and saidit pressurechecked good. They replaced the radiator cap. Now I am losing much more coolant then at that time.
Suspect a head gasket, cracked cylinder or warped cylinder head. Are there any other possibilities? Assume my next step is taking it to the garage.

 

Blown head gaskets on miata engines are very very rare but not totally unheard of. A block checker can verify it if so,however the throttlebody has coolant running through it and could be leaking directly into the intake as well as an intake gasket leak.