Datsun 1200 came with a 13 pound radiator cap. The spring-loaded cap regulates the cooling system pressure, as water under pressure will boil at a higher temperature. Higher temperature equals more efficient cooling but too high a temp and the water boils, which reduces cooling to zero.

[[Radiator#174_5cfc05a673eda.jpg|]]radiator

Pressure Cap

Use a 13 lb cap as per original specification. The Nismo high-pressure 18.2 lb (1.3 bar) caps are solely for 100C-degree (212F) thermostats. A lower pressure will help prevent leaks in the radiator, heater core and hose connections.

Push-button Cap

Nissan "push button" cap

21430-16300 ラジエーター押スキヤップ

Album 21785

aftermarket PUSH cap

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Extra high-pressure

Extra high-pressure caps allows you to run a higher temperature thermostart where the engine to runs above normal boiling point of the coolant. The extra high temperature means the radiator sheds head faster (larger temp differential to the air). This means a smaller radiator will be adequate.

The downside is that old radiators, heater cores and hoses may not be able to handle the pressure and may start leaking.

Nismo | Kameari

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