In other words....the antifreeze shouldn't be right up to full, unless you have an overflow connected to the rad. Dutchy
antifreeze is slippery stuff, might try re-tightening the clamps when the engine is hot, surprising what an eighth turn will do - also make sure the rad isn't overfilled and developing too much pressure and that the rad fittings haven't been dinged at all, and if necessary, a light wipe of #2 Permatex does wonders
Bill