Coolant Fluid and Radiator Caps?

Question

Why is the coolant fluid in an automobile kept under high pressure? Why do radiator caps have safety valves, allowing you to reduce the pressure before removing the cap?

Thanks for any help =)

Answer 1

When you pressurize the coolant it has a higher boiling point, the safety valve allows you to vent the pressure in a controlled manor, as opposed to allowing all the pressure to escape at once, likely causing the coolant to erupt out the top of the radiator and burning you.

Answer 2

The pressure keeps the coolant moving through the engine and radiator so it doesn't stay stagnant and overheat. The pressure valve is a safety thing so that if you have to take the cap off it doesn't explode on you.

Answer 3

Its not reallly high pressure but it is more like low pressure,,but above atmospheric.

By allowing pressure in the system you raise the boiling temperature of the coolant mix. It also allows the passing air and radiator fan to remove heat easier and faster.

Water boils at 212 at sea level ( 15 lbs per sq in.)

Now puit on a 15 lb cap. For every lb on the cap the boiling tem is raised more than 1 degree. So now the water boils at ---212 + 15 = 237 degrees. That means bo steam in the coolant  cavity or radiator---- which would interfere with the water pump circulating the water.

I hope this gives you some idea of whats going on.

Answer 4

The coolant is kept under high pressure because the heat of the engine instigates the ever increasing pressure of fluids inside the engine, so, you need the radiator caps to give  you the safety of reducing the pressure before  you remove the cap.  As one who was severely burned back in the 1970's by an over-eager, and very impatient and discourteous  driver who yanked off the cap as I was hosing down his radiator on his Dodge Challenger, a well known high-performance car back then, I can assure you that you'd better be very greatful that cars have those reserve tanks to fill in more fluid rather than just the radiator caps, safety-valved or not, of old.  I can guarantee you that you do NOT want that hot water spewing all over you and your now wet clothes clinging to your body with super hot water as  you go running for a cold water hose for relief.   To add insult to injury, a couple of weeks later that same customer in his same purple Dodge Challenger came back to our gas station and said he wanted to buy  a couple of dollars worth of gas (prices were MUCH cheaper then), and I was so mad at him  that I forgot to let go of the pump handle as the $2.00 price came around, and I ended up buying HIM a full tank of Premium gasoline out of my money because of my anger.  Be  thankful for the protection you now have.  You DEFINITELY wouldn't want the experience I had.  God Bless you.