When a car is overheated when is it safe to open the radiator cap?

Answer 1

it is best to let it cool off first with caution it can be removed hot I don't recommend it. to the easiest way to check to be sure if it is cool enough squeeze the upper radiator hose if it doesn't have any pressure in it it will feel soft. That's when it's safe to remove the cap. I would still use a rag just to be sure when removing a hot cap.

Answer 2

Very tricky one, this. It can also be extremely dangerous and I am not kidding you. So here's lots of detail.

The cooling system is pressurised, because the higher the pressure the higher the temp at which the water boils. You've heard about people in high mountains where they can't make a good coffee because the water boils at too low a temperature? Same reason but the other way.

EDIT: Lower pressure than at sea level: low boiling point. Higher pressure -- higher boiling point. Some races cars run fifty or more degrees over normal boiling but they don't 'boil'. Very high pressure cooling system. But when they pile up and smash the radiator -- stand back!!

Anyway...The problem is that even when you no longer hear the coolant bubbling around inside the engine or the steam has stopped hissing out past the cap, it doesn't mean it's safe. If you open the cap too soon, while there's still a lot of pressure in the system, the water instantly super-boils and flashes into steam and you can scald yourself VERY badly.

Pople get BLINDED this way and I do NOT want that to happen to you!

If you need to get going again fairly quickly one of the best tricks is to pour or better still splash/spray some water onto the radiator core, through the grille if you have to. The exces heat goes into this water and helps to cool whatever's still inside the system.

Then, to remove the cap, cover it with a heavy cloth and preferably wear work gloves. Lean back away, and also turn to one side. You do NOT want to get blasted with super-hot steam down below the waistline, okay? Now, grasp the cap firmly and try cracking it open just a touch. If things start getting pretty violent again (like you hear major bubbliing going on) shut it again and wait a bit longer. Spray more water on the core and so forth. (Note: It actually often helps if the engine is just ticking over with the car in park -- or in neutral on a manual. I'll explain why in a second. And don't forget to put the hand brake on to be safe, too. You don't want to be standing in front of a car when it pops itself into drive...Rare, but why risk it?)

So you've waited a bit longer. Very carefully open the cap. The thing will most likely still bubble like something in Yellowstone Park. DON'T lean over it to have a closer look! (Not kidding. I've seen people do it and then just like Old Faithful it goes up in their face.)

Now you need to add water or coolant. With the engine just ticking over, pour the coolant in. Just a cupful or two. Stand back and wait a few seconds and watch most of it blow out again. Thats okay. It's normal. Gets messy but never mind. Then add some more, and keep adding until it settles down.

Why have the engine running when the thing's already hot? Simple. The engine has a pump to circulate the coolant. Engine off? No pump. Lots of nice cool coolant in the radiator and nothing in the baking hot motor. Result? The moment you start up it'll all get pumped through and probably just go to steam and you are back where you started. And also, by adding it gradually with the motor idling, you don't 'shock' the engine block and cylinder head with cold water.

Ever put a hot jar in cold water?

Same problem. You can crack the head -- and maybe even the block. Expensive, you know.

So now it's all filled up. Head for someplace where you can get the thing fixed or at least patched up. If it's overheating there'sa reason. You can cook a motor real quick otherwise and it'll cost thousands to replace.

A hint: If you are driving in hills and the car overheats on the uphill, when going downhill run a trailing throttle (no gas) so the motor is burning minimal fuel. The less fuel you burn the less heat you get. It'll cool faster.

Good luck and BE CAREFUL!

Lenky

Answer 3

Please do or have carried out a pair of issues right this moment: #a million. Have an low-cost *cooling gadget stress attempt carried out which exams for exterior or inner coolant leaks. #2. in case you allowed the engine to expire of motor oil i'm making a guess the undesirable cooling gadget has by no skill been drained, flushed and *wiped sparkling. in case you have somewhat mechanical ability it rather is basic to splice a height or Prestone flushing T into the heater hose that runs from the water-pump to the heater-center. while the flushing eater is obvious, drain the block and radiator. eliminate and sparkling the coolant restoration tank with warm water and Wisk utilising a great around kin brush. installation one 33 oz. bottle of Prestone great Radiator cleanser interior the radiator and fill the relax area with sparkling water. *stress the motor vehicle a minimum of 200 miles with the cleanser interior the gadget & watch the temperature gauge. If the gadget nevertheless gets warm you're six years overdo for a radiator alternative.

Answer 4

if you have a water hose close by you can cool it by running water over the radiator to cool it manually then it will be safe to open it up but as stated earlier use a thick towel or rag over the top then start car before putting water in radiator

Answer 5

I've opened them with heated engines. Throw a damp rug over the cap first, then very slowly start truning the cap until the pressure is completely released.

Answer 6

About an hour, but just in case it is not cool enough, use a towel over the cap as you remove it.

Answer 7

When it cools off. Give it 30 min to an hour.

Be careful. You can do some serious damange to the engine if you let it over heat too much, too often.

Answer 8

Also, best to open it with a rag or towel to catch any water that may spew out in case it's not cool enough

Answer 9

It is safe once it has cooled down to a normal temperature.

Answer 10

Please give it ample time to cool before trying to remove it. It could be an hour or more. Beats a face, or handful, of steam.