Stant pressure release cap?..
Note: Top Right hand corner.
did mine.. it has a red pressure release valve on the cap.. this way everyone in a while you can release any bubble build up.. but do not do this while the engine is running or hot.. In a sense instead of opening or taking off the cap.. you simply lift up the red handle to release any build up then make sure it's set back down in the correct location.. it may take several times of correcting the balance of antifreeze in the reservoir or actually adding more antifreeze int the radiator.. Just depends on how low the fluid is upon removing the cap.
: Place a worn out rag on the cap opening after removing the cap itself just so you don't end up with a mess all over the radiator etc.. then gently squeeze the top hose as well as the bottom hose. Over time this will work the bubbles out of the antifreeze. Ever since we've done this (new cap and the squeeze thing) we've not had an issue.
Lately.. Upon removing the old cap or any cap.. check the rubber seal that mates up with the radiator.. If the seal is going bad.. it can leave rubber seal fragments on the radiator opening as well as on what's left of the seal.. thus causing an uneven mating of the seal and could actually be allowing air into the system which in turn is causing the air bubbles..