Quote Originally Posted by jick.cejoco View Post
be careful with those aftermarket radiators that come with a radiator cap. the pressure throat is usually deeper than the original and the pressure valve does not seal. this could potentially prevent the antifreeze/coolant from returning to the radiator from the surge tank/recovery bottle/overflow bottle. the typical non closed circuit cooling system(pressure cap not installed on the radiator) have radiator caps equipped with pressure valve to pressurize(hence raise the boiling point of the coolant) and a vacuum valve to allow the displaced coolant due to expansion back to the radiator. the upper seal of this type of radiator cap also has an upper seal to keep the vacuum while the coolant returns to the radiator. on turbocharged subarus, there are two raidator caps, one for the turbocharger coolant tank and one on the radiator. these two caps do not have the same pressure ratings. the radiator mounted has a rating of nominal 1.3 bar while the one mounted near the turbocharger has 1.1 bar of pressure. the ones with closed system cooling system do not have a vacuum valve like the ones for a toyota previa or most newer chrysler products
it shouldn't be difficult to design fillers/caps that offer good sealing.
so i wonder, is this non-sealing cap by design, poor choice of cap, or simple poor workmanship?