Defective radiator cap: 3 indications

Overheating
Overheating is one symptom indicating something is amiss with the radiator cap. Coolant won’t flow correctly to the engine if the car’s radiator cap fails to maintain pressure within the cooling system.
If the radiator cap is unable to seal the radiator, it may allow air to enter the vehicle's cooling system. In this case, the cooling system will struggle to maintain an appropriate working temperature.

Leaking coolant
Expect your automobile to puke coolant when the radiator top itself has poor gaskets. Being trapped and unable to vent, the build-up pressure may force the heated fluid out from the radiator. I once have to take my Honda civic to a repair shop to get it fixed because of this.

Failed radiator hoses
The vehicle’s radiator hose can potentially collapse due to a malfunctioning radiator cap. This might happen while the radiator is cooling down, further damage the hose structurally.

Hoses can bulge and eventually tear up if a radiator cap fails to vent, redirecting coolant fluid toward the car’s reservoir.

Before you go out and buy a new radiator cap, remember to check it's compatible with the vehicle. If in doubt, examine your car's manual, or you can even call the dealership where you bought it.

 

My cars radiator cap was recently leaking, replaced it, all good now.