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Car encyclopedia

Radiator Cap

The radiator cap seals the main filling point of the cooling system. It also allows a set pressure to build in the system, which increases the boiling point—and thus, the efficiency—of the cooling system.

Symptoms of Wear or Failure

  • Coolant may leak or boil over
  • Temperature gauge may get really high
  • Illumination of the engine temperature warning light
  • Engine may run hot or overheat

Related Repair Advice

  • The term "radiator cap" refers to the cap that regulates the coolant pressure in the cooling system. Standard pressure is usually 14 to 16psi.
  • The cooling may have multiple "radiator caps" located at the various fill points
  • Whenever the cooling system is serviced for any reason, the radiator cap(s) should be inspected and replaced as necessary

Be very cautious when removing the radiator cap. Don't remove the cap when the engine is hot.

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