why it's wrong to add water to the car radiator while the engine is warm and not running ?

Question

it's two thing which is right first to add water while the car is cold or second while the engine is warm but running ? can some body explain why?

Answer 1

You do need to let the pressure off the cap slowly so the hot water doesn't scald you!
But to answer your question about not adding cold water to a hot engine that is not running.
The reason to have the hot engine running when you add the water is so that the cold mixes with the hot and cools the engine down slowly!
If you fill the radiator with cold water and then start it, when the thermostat opens all the cold water will hit the engine at one time!
Such a drastic and sudden change in temperature can blow a head gasket or in some cases crack the head! This is a very costly repair!
Hope that helps!

Answer 2

It is not wrong to add water to a warm engine. It is only that the pressure in the radiator must be reduced first and safely. The layman cannot do this safely and that is why manufacturers take the safe way out and tell you to add when cold.

Most times, if the plastic reservoir has water in it, the only thing needed is to fill up the reservoir to its high mark level. That is sufficient and should be done cold. When the thermostat opens the water will be sucked in, if there is a need. When the water temperature rises, the excess water on expansion is channeled back into reservoir. The water is sucked back into the system when it is cool. In this manner, the water need not be refilled regularly. A check once a week is sufficient for a secure and non leaking system and water is only needed to compensate for evaporation from the reservoir.

However, if you have allowed the water to dry out in the reservoir, you will need to open the radiator cap.Do this when the engine is touch warm or cold only. Fill the water to the top. Do not replace the cap yet. Keep it on a safe place away from the car engine. Start the car and let it idle until the water is running through the system. You can see the water swirling across the neck of the radiator when the engine is warm. This is when the thermostat is open. Fill up the radiator until the neck of the radiator if needed. Do it carefully as the engine is running and is a potential danger to you. After you have done so, stop the engine, replace the radiator cap firmly and fill up the reservoir to the high level mark. Now, you are well and ready.

The reason for the engine running technique is to allow the thermostat to open and any trapped air to be expelled. Air is seldom trapped but when the level of the water is low enough you can have trapped air. Too much bubbles of air is not good in a radiator system.

One last thing, check the water level in the reservoir everyday for a week. Any serious loss of water could mean a leak somewhere in the system.

By the way a cold running engine is not as efficient as a fairly warm engine.

Answer 3

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Joys of old Cars.....Other than it being a Ford, Yes the spark plug wire off would cause loss of power, some overheating, misfires, etc. You could have damaged the number three cylinder or head by driving it too long and overheating. Before assuming the worst, if it seems to be running hotter than normal, first check the antifreeze level and weight (With an Anti Freeze tester). If Okay, leave the radiator cap off, and start the cold engine. Leave it running and watch the Anti Freeze in the Radiator cap opening. You should see it start moving in the Radiator within 10-15 minutes after the motor warms up. If it does, then the thermostat and water pump are okay. If not, then replace the thermostat first. If that doesn't correct the problem, then the water pump is next. If the Anti Freeze is moving when the engine warms up, but the level drops way down in the radiator, then you are low on Anti Freeze. Add more Anti Freeze (Not Plain Water) and fill to within one inch (2.54 cm) of the filler neck. If everything appears okay with the radiator, but still too hot, your thermostat can be changed from 180 Degree F down to 140 Degree F. This will allow the coolant to enter the engine at a lower temperature. If you have an Electric Cooling fan, make sure it is working on the radiator. Most have a relay switch connected to a thermocouple to kick it on when the motor reaches 220-240. If you have a real temperature gauge in lieu of the "Idiot Light", pay attention to the temperature. Highway, the temp should average 110-180. In traffic and idle, 200-220 but should cycle the cooling fan on and off. The hole in the exhaust may or may not be a problem. I would seal it just to prevent fumes from coming into the car to kill you or make you retarded from the Carbon Monoxide. If the Catalytic Converter or Exhaust is stopped up, Then the engine would sound like it was running hard and strong, but you wouldn't have any power. The exhaust should be flowing out under good pressure, if not I'd say the Catalytic Converter should be replaced first. If you ran the tank dry, especially fuel injected, if the fuel filter didn't catch it, then the injectors could be clogged. You can yank the fuel rails off, clean the injectors by hand, or spend $50 and let the local shop or dealer pressure clean them while still mounted. They just disconnect the fuel line at the back of the fuel rail, and pressure clean them from there. Good luck, older cars never have just one single problem.

Answer 4

Your problem sounds like a converter problem if a vehicle is running rich to much fuel it will eat up the inside of the converter and will also code the 02 sensor it eventually will clog the exhaust and you will get a bad idle and as it gets worse you will loose a great amount of power and it will seem worse the farther the car is driven. You do not need the factory converter you can use an aftermarket and it will be just as good. The plug wire being off will defiantly make it run like crap being a 4cyl. it would be very noticeable, verses an 8cyl vehicle. It will retain heat for a good while but if the converter is clogged it will be noticeable hotter for the exhaust is having a hard time escaping. I would have a good injection cleaner run through it not the one you buy in a can. I am talking about one that is a two to 3 part system cleaner which will clean the throttle body and valves etc of all carbon build up. At my shop we get 80.00 labor and the cost of the two cleaners that are run straight into the throttle body and then a can of cleaner is added to the tank it is a three part system that works really well wynns sells it you would need to check with your local shop and see if they do this. Personally i would have the converter changed and see what kind of improvement you get it may be all you need.

Answer 5

If you add cold water to a warm engine that is not running you run the risk of the engine block cracking when the cold water hits the hot metal engine block. Because an engine that is running is making it's own heat, the cold water gets warmed up quickly and probably won't crack the block. Really it is best to fill the coolant when the engine is cold and then top it off when it gets warm and the thermostat opens.

Answer 6

Water For Car Radiator

Answer 7

Weather hot or cold doesnt matter if your adding it to the reservoir

If you have to actually add it to the radiator never do this while the engine is hot, when it's hot the water is under pressure and will shoot out of the cap and send you to the hospital with nasty burns
I would never add while it's running because the water will be hot and moving around because of the engine pumping.

As far as cracking the block due to overheating is concerned why not shut off the car and pour the water ON the radiator instead of into it?

Answer 8

Add coolant or water when the engine is warm and running if you're pouring it into the radiator so the whole cooling system will get filled.

If you're just adding to the reservoir, it doesn't matter.

Answer 9

When cold water hits hot cast iron it can crack, and that's bad. With the motor running it keeps the coolant mixed. New cars use a fill can and you don't put water directly into the radiator so it isn't as critical as in old cars.

Answer 10

You should add coolant to the reservoir, not directly to the radiator (unless you have a really old car). You just want to make sure not to open the pressurized radiator when it is hot. You can be scalded or worse if you do.