How long should it take until there is no more pressure in the cooling system after you shut off the car? Should there be no pressure at all when you open the cap the next day after it sits all night?

 

there should not be any pressure after it cools

 

The pressure in the system is almost directly related to the temperature, at least unless something (or someone) opens a cap and relieves it.

I would start by touching one of the rubber coolant hoses. If that's cool, try touching a metal housing. If that's not hot, the coolant is safely cool enough to open the cap. Still I use a couple of rags over the cap when I loosen it to be absolutely safe.

Dave

Dave

 

Well it felt like and sounded like it had almost the same amount of pressure as it does when you shut off the car. It was a little low on coolant too.

 

You mean it sprayed everywhere and burned your skin?
Does it suck air in slightly?
Are you concerned something is pressurizing it beyond the simple principles of the coolant system?

 

No, the next day when it was cold, it still had a ton of pressure. But today it was okay after it cooled. Both times it was full of coolant before I started it, maybe it just had some air in the system before. Today it did sound something like sucking a small amount of air in, or letting a little out, when I opened the cap, and the radiator hose was not stiff (pressurized) like it was last time.