bubbling?
that doesn't sound good, is it consistent bubbles coming out?
do you see any almond colored residue in the oil cap and pull the dipstick and does the oil look clear (if new) or normal dark color (if it has been a while since an oil change)? If it has a milky almond color?
If milky or almond colored you probably have a blown head gasket between the cooling jacket and cylinder making it push compression into the cooling system causing those bubbles. and some may be getting into the engine oil.
I just replaced a head gasket on a lift doing that same thing.
it had a mazda FE series engine in it. (yours may be the same engine).