The radiator cap will get hot if the coolant is near the cap. Caution should always be taken when removing it to avoid being burned. The maximum coolant level is below the cap, but the cap pressurizes the system. Removing it too quickly without allowing the pressure out can result in serious injury.
A radiator cap can not only be hot, but it is holding in pressure. When the cap comes off under pressure, hot antifreeze will spray out, possibly causing injury.
On most cars if they don't have a radiator cap, then you can put it in the cooling system by pouring it in through the upper radiator hose. Even if you are suppose to do this while engine is hot DO NOT because it will have the same affect as pulling the radiator cap while hot.
There is a white tank up by the passenger's side fender. This is the reservoir for the radiator. Do not remove the cap while the coolant is hot. The radiator itself does not have a cap on it.
The radiator cap may not be getting hot because it is located in a separate reservoir from the radiator itself. It is designed to maintain pressure within the cooling system and does not directly contact the hot engine coolant.
It could be that the radiator cap is not able to maintain pressure. Check the radiator cap for cracks or any other damage. Replace if necessary. DO NOT remove the radiator cap when the engine is hot.
Hot water in the radiator is under pressure and can burn you.
Do it when the car is cold if the radiator is hot fluid may be forced out when you take off the cap.
most likely it will be hot so put snow on it
If you have a "Leak" from the cap either the cap needs to be replaced or the top of the Radiator is damaged. It is normal for thermal expansion (water gets bigger when hot) to cause the coolant to go into the expansion tank when cars is hot and to be drawn back into the radiator as the engine cools
Remove the radiator cap when the engine is cool and add the coolant into the radiator or you can add to the coolant overflow bottle. DON'T remove the radiator cap when the engine is hot!!!
If the cap on the Resoivoir twist or turns on says DO NOT OPEN HOT and there is no cap on rad then this is where you fill it at.
A hot radiator releases excess coolant through the spring-loaded cap in to the reservoir, and when cooled the partial vacuum created by cooled radiator pulls it back in. A reservoir should be only about 1/4 full cold on a system that uses a radiator cap, some cars have a pressurized cap on reservoir and no cap on radiator