Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Radiator Caps: Description
The radiator cap consists of a pressure valve and a vacuum valve. The cap has several different functions: It prevents coolant loss when vehicle is in motion; prevents impurities from entering cooling system minimizing corrosion; allows atmospheric pressure to eliminate the vacuum that occurs in system during cooldown; and raises coolant boiling point approximately 2°F per psi of pressure by maintaining a constant cooling system pressure. For radiator cap testing specifications, see appropriate manufacturer's article in this section.
Cap should maintain constant cooling pressure in system.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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