Radium Radiator Cap, Type-A, 1.1 Bar (16 psi), Black

Radium Engineering Radiator Cap, Type-A, 1.1 Bar (16 psi), Black - Part #18-0076-A11

A radiator cap is the cheapest part in the cooling system and the one most people never replace, and a tired spring or a hardened rubber seal is how a K-swapped EG ends up pushing coolant into the overflow every hot lap. Radium's Type-A cap is a stainless cap with silicone seals and a 1.1 bar spring, sized for the small 32mm neck on the 88-91 Civic and CRX, 90-93 Integra, 92-01 Prelude, NSX, 2016 and up Civic, and every Radium expansion tank.

What It Is and Why It Works

Pressure raises the boiling point of coolant, about 3 degrees F per psi, so a 16 psi cap lets the system run past 250 degrees without boiling and keeps the water pump from cavitating on hot restarts. Radium stamps the cap from stainless steel and black electroplates it, and replaces the natural rubber seals of a factory cap with silicone, which doesn't harden and crack after a few years of heat cycles. Type-A is the small-neck cap: a 32mm inside diameter neck with the short ear spacing used on older Hondas, the current Civic, and Radium's own expansion tanks. Type-B is the larger-ear cap found on 92-15 Civics, 94-06 Integras, the S2000, and most 90s and 2000s Hondas, and it is a different part.

Specs

Fitment

This cap does not fit Type-B necks: 1992-2015 Civic and del Sol, 1994-2006 Integra, 1994-1997 and 2004-2008 Accord, 2000-2009 S2000, Element, and Fit. Radium makes the same cap in Type-B; ask us if your car is on that list.

What to Know Before You Buy

Match the style before the pressure. A Type-A cap on a Type-B neck won't lock, and vice versa, and the neck style follows the radiator, not the engine; a K-swapped EK with the factory EK radiator still needs Type-B, and one with a Radium expansion tank needs Type-A. Radium also offers this cap in 1.3 bar and 1.5 bar springs. Go higher than 1.1 only if the radiator and hoses are up to it; a higher cap fixes boil-over, not a cooling problem. If the old cap was weeping, look at the neck seat for corrosion before you blame the cap.