You're losing coolant somewhere if the reservoir is being emptied on cooldown. Ideally, it should stay about half full and the radiator should stay entirely full- - - -no air at all in the top tank.
Jerry
Yes, I’m definitely losing coolant out the overflow of the puke tank. But I presume that now to be a symptom not the cause. The cause being air in the system.
Is this the style cap you’re referring to?
https://www.oreillyauto.com/detail/...76/murray-4-psi-radiator-cap/mcs0/100205
