A bad radiator caps can cause a lot of cooling system problems.

You may think, the only purpose of your radiator caps is for adding coolant to the radiator, but it is not.

Your radiator caps is much more important than most people understand and while adding coolant to prevent overheating is important, it is not a true picture of all your radiator cap does for you.

  • Allows you to add fluid
  • Seals your cooling system
  • Allows pressure to build up to a specific point in your cooling system
  • Raises your cooling system boiling point to prevent overheating
  • Vents excess pressure to protect cooling system components from damage
  • Transfers overheated coolant into an overflow bottle to prevent fluid loss and air pockets
  • Creates a vacuum to recapture vented coolant as your system cools

There are a few ways to detect if your radiator caps is malfunctioning. Below is a list of what to look out for.

Engine Overheating

  • If your engine is overheating, there more than likely is a problem with the coolant and it leaking. As the engine temperature rises, make sure to turn off the car before you inspect under the hood. Once the engine is cool, you may notice coolant around the cap. The coolant could be escaping because of the radiator pressure caps. Inspect it for any damages.

Coolant Leak

  • A stuck radiator cap will not be able to release fluid, allowing pressure build up. As a result, This pressure can cause the radiator hose to burst or create leaks.
  • Check for any coolant leaks coming from around the caps or the radiator. If there are any holes in the radiator, inspect the caps for any defaults as this can be a sign it is needing to be replaced.

Boil Over

  • Your vehicle’s reservoir tank contains coolant. The pressure in the radiator releases the cap and sends the fluid to the tank. Consequently, If your caps is not functioning correctly, the coolant will be released to quickly and can overflow the reservoir tank. If you experience this boil over, check the cap for damage.

Air in the Cooling System

  • If the radiator pressure cap is not on correctly, air will enter the cooling system. When the air enters, it creates smaller compartments of air inside the hoses, heater core and thermostat. The heater will be unable to function because of the air and will cause overheating. Buying the correct radiator pressure caps can easily help prevent this problem from happening.

Collapsed Radiator Hose

  • If your radiator hose has collapsed, this could also be a result of a faulty cap. So, If your radiator cap does not let go of the vacuum the way it is supposed to, you could see it affecting the radiator hose as it cools down. Again, check your radiator pressure cap for any damage and replace as soon as possible.


Rad Caps
Rad Caps

So, If you are ever in doubt about your rad caps just replace, They are cheap !