One that seals at the top neck and one that seals at the bottom of the filler neck. In the same way avoid opening the hood of the engine if steam is coming out as that can also cause a scalding injury.

6 Symptoms Of A Bad Radiator Cap And When To Replace
How to tell if radiator cap is vented. As the fluid heats up it expands. If incorrect replace the cap. It eventually over powers the primary spring in the radiator cap. How a car radiator cap works. Air in the cooling system. If you suspect your radiator cap is leaking you can first remove it and inspect it.
Ways to check if your radiator cap is causing problems on your car. Replace the cap if the seals are cracked hardened or damaged. The bottom seal is broken as the pressure exceeds the spring force of the cap and the cap rises. Of course never do this when the vehicle is still hot to avoid getting a bad burn. Look at the bottom of your radiator cap. How to tell if your radiator cap is faulty.
There are several warning signs that your radiator cap is not working right. There are two seals. All radiator caps will vent air fluid pressure out when the pressure reaches their rated number 13 psi etc vented caps have an additional incoming vent which will allow them to draw coolant back in from the overflow tank when the radiator cools down and there is vacuum. Look up the pressure rating specified for the vehicle and compare it with the pressure rating printed on the cap. If your coolant is leaking it could mean your radiator cap is bad. Your engine is overheating.
If you notice coolant near the radiator or the radiator cap then you clearly have leaky coolant. The cap will not allow air or coolant to expand out of the radiator untilthe design pressure is met 7 or 13 lbs depending on model at whichpoint you may have an overheating condition. You have a coolant leak. Check to see if the radiator has holes in it or if the cap looks worn or damaged. If your temperature gauge starts reading high your radiator cap could be at. Visually inspect the condition of the main seal pressure seal and return seal.
If the cap isnt. Coolant overflow not on proper level. 1 leaking coolant if the radiator cap is stuck pressure may build inside of the radiator which could cause cooling system components to leak or burst. Noticethat the poppet at the bottom is spring loaded and thus normally closed.