72 Vent cap or no vent cap (radiator)

[Eric Fairclough]

Does anyone reccomend using a vented radiator cap? I have a standard 16 pound cap on mine now. Mine has the copper 454 expansion tank. Thanks Eric

[Duke W.]

Re: 72 Vent cap or no vent cap (radiator)

I'm not sure what you mean by a "vented radiator cap". Modern radiator caps are designed to hold pressure up to a certain point and 15 PSI has been the norm for about 30 years. Allowing the cooling system to build pressure increases the boiling point. For example, with a 50/50 glycol-water mix and a 15 psi cap the boiling point is 265 deg. F. Once boiling occurs the 15 PSI is exceeded and the cap valve will open allowing vapor to vent, and it will usually include some liquid coolant, too.

Gasoline caps can be vented or pressure/vacuum relief like a radiator cap. Older cars without evaporative recovery systems typically have vented caps. All evaporative emission systems include a cap with both pressure and vacuum relief valves that typically open at about one to two PSI pressure or depression.

Duke

[Duke W.]

Re: 72 Vent cap or no vent cap (radiator)

I'm not sure what you mean by a "vented radiator cap". Modern radiator caps are designed to hold pressure up to a certain point and 15 PSI has been the norm for about 30 years. Allowing the cooling system to build pressure increases the boiling point. For example, with a 50/50 glycol-water mix and a 15 psi cap the boiling point is 265 deg. F. Once boiling occurs the 15 PSI is exceeded and the cap valve will open allowing vapor to vent, and it will usually include some liquid coolant, too.

Gasoline caps can be vented or pressure/vacuum relief like a radiator cap. Older cars without evaporative recovery systems typically have vented caps. All evaporative emission systems include a cap with both pressure and vacuum relief valves that typically open at about one to two PSI pressure or depression.

Duke