Radiator issue

[TheNewt10]

Lately while driving I've noticed that hot air has been coming out of my vents. And when turning off the car i hear water boiling in the radiator container on the side. Water then comes out. Is this normal? Does anyone know what can be the problem? BTW right now there is only water in my system no antifreeze

[oyajicool]

Go through with cooling system check up, like thermostat, radiator cap, radiator hoses to begin with.

[kinguin7]

Most likely culprits are a bad radiator cap or a blown head gasket. Go to an Advance or Autozone to see if you can rent a radiator pressure test kit for starters.

[Stormtrooper]

Is this normal?

Definitely NOT normal.
You're engine is overheating.
You can cause damage if you drive it like this.
How long has this been going on?

The thermostat could be bad.
Does the engine lower it's idle speed after it warms up? (around 1 or 2 minutes after cranking?)
Is your engine cooling fan working properly? It should come on when the engine gets hot.
Do the hoses between the thermostat and radiator get hot?

These are a starting point.

If you're unlucky, your water pump may be bad. But there are other (cheaper) things to check first that will hopefully fix the problem.

Also, is the water in your radiator clear/clean?

EDIT: And kinguin7 is right. It won't hurt to go ahead and replace the radiator cap. I would do this FIRST.

[BurtonRiderT6]

The only way coolant can blow out through the over flow tank is because its either not holding pressure when it gets up to normal operating temp...because you have a bad cap.

OR...you have a blown head gasket and the associated piston is pushing air into the cooling system on the compression stroke. Check to make sure coolant hasn't mixed with the oil. This will be a little more difficult as you are running straight water so you may not get the milky gray color on the dipstick (common sign of a blown headgasket)

OR........you have a very slow leak or a pinhole leak that is pissing coolant out while you're driving......then when the engine is shut down and cools, air gets sucked in through that small leak. Then after so long, as that air space grows in the cooling system....it can no longer stay cool while your engine is running and the overpressure gets pushed out through the cap and goes into the over flow tank.

Try a new cap.

Definitely NOT normal.
You're engine is overheating.
You can cause damage if you drive it like this.
How long has this been going on?

The thermostat could be bad.
Does the engine lower it's idle speed after it warms up? (around 1 or 2 minutes after cranking?)
Is your engine cooling fan working properly? It should come on when the engine gets hot.
Do the hoses between the thermostat and radiator get hot?

These are a starting point.

If you're unlucky, your water pump may be bad. But there are other (cheaper) things to check first that will hopefully fix the problem.

Also, is the water in your radiator clear/clean?

EDIT: And kinguin7 is right. It won't hurt to go ahead and replace the radiator cap. I would do this FIRST.

How do you figure his engine is overheating? Thermostat's keep engine temps between 190-215 degrees on average. Water boils at 212 degrees and he is running straight water.

The fan doesn't come on just when the engine gets hot. It will come on if the car reaches a dangerous temp. Typically when sitting at idle on a hot day when there is no airflow.

The hoses and radiator are going to get hot, hence the warning sign on the cap about opening while hot.

A good way to check the water pump and thermostat is to run the car with the radiator cap off and as it gets close to operating temperature you should watch the water/coolant. Once the thermostat opens you should see the coolant start to flow. If it doesn't then you may have a thermostat or water pump problem. If it's not overheating then it's not a thermostat or water pump problem.

[Stormtrooper]

How do you figure his engine is overheating? Thermostat's keep engine temps between 190-215 degrees on average. Water boils at 212 degrees and he is running straight water.

Because I did not know that I do now!

The fan doesn't come on just when the engine gets hot. It will come on if the car reaches a dangerous temp. Typically when sitting at idle on a hot day when there is no airflow.

By 'dangerous temp' do you mean the high end of the desired temp range? As in 215 degrees, if 190-215 is desired?
I guess I meant to say 'when the engine gets too hot'. I mean, I know the engine is supposed to be hot.

The hoses and radiator are going to get hot, hence the warning sign on the cap about opening while hot.

Yes, I know. Haha. But if one isn't hot, that's a good sign for a stuck thermostat. But of course, if his engine isn't overheating in the first place, then not to worry!



Lastly, if the system is not holding pressure, will that not lead to overheating?

[H311RA151N]

x2 On everything BurtonRiderT6 said.

Cap, Headgasket, small leak. Id put $5 on it being a bad cap.

[evil_demon_01]

How do you figure his engine is overheating? Thermostat's keep engine temps between 190-215 degrees on average. Water boils at 212 degrees and he is running straight water.

The boiling point of water increases when put under pressure.
That is why the cap is rated to a certain pressure.



The system can be over heating, (the thermostat could be stuck shut, or the water pump fins gone) Which would mean the radiator would have almost no effect, and the engine would overheat.

Which could result in the water boiling and exceeding the cap pressure thus pushing past the radiator cap.

[antonio7566]

Use some coolant your car needs it for more than one reason, and make sure your system is well bled. That's where I would start, a gallon of antifreeze mixed with water is really cheap most places use a 50/50 mix.

[BurtonRiderT6]

The boiling point of water increases when put under pressure.
That is why the cap is rated to a certain pressure.



The system can be over heating, (the thermostat could be stuck shut, or the water pump fins gone) Which would mean the radiator would have almost no effect, and the engine would overheat.

Which could result in the water boiling and exceeding the cap pressure thus pushing past the radiator cap.

OR his cap could be bad/damaged resulting in a leaky system in which the car would not pressurize causing the water to be able to boil at 212 when the car is turned off. The water in the overflow bottle could be vapors heading to the top of the radiator and making their way out. If his car is not overheating then my money is on the cap.....especially since it's the cheapest fix.