2007 dodge magnum repaced radiator now the reservoir is boiling and spitting out water while the car is running/idling water is jus bubbling up out of the reservoir what could this be

check coolant level fan operation and water pump

If it is a constant bubbling while running and at that same time the engine is not overheated,you may need a head gasket replacement.

Pam are you sure it's boiling? If the Antifreeze is boiling I'd think you'd see steam coming out of your reservoir as the water expands into the reservoir, but you didn't say you see anything like that.
Of course engines get hot, that's why we have the cooling systems but it doesn't sound like it's "boiling" to me with no signs of visible steam unless your antifreeze level is really low?

If it's really boiling, and you antifreeze level is good, then your reservoir should be getting filled up with expanded hot water that goes into it to catch it when it expands.

If the water isn't going into the reservoir, then maybe your antifreeze level in the radiator is too low and you need to add antifreeze?
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Best to fill the radiator with the engine cooled down. If you ever have to open the radiator when it's hot, NEVER open it with your bare hand as you could get scolded with boiling water. Instead use a big thick towel to remove the radiator cap off a hot engine. Again, if you can, just wait until the engine cools then open the radiator cap.

With the engine cool, you can fill the radiator with a 50/50 antifreeze mix. The 50/50 mix come premixed 50 percent water, and 50 percent antifreeze. So you can throw that stuff straight into the radiator.

Non mixed antifreeze needs to be mixed 50/50. Some people use 50 percent distilled water when they mix it because distilled water doesn't have the minerals in it that may get stuck in your radiator. That's being a bit picky about it though. Tap water works fine in a pinch. The other 50 percent is antifreeze. You can mix it right in the radiator too, put in a measured amount of the antifreeze, followed by the same measured amount of water. The water pump will mix it all together when you run the engine.

Put the cap back on and run the engine and if/when the water "boils" it should go into your reservoir. If it does boil in go in the reservoir then yes...your engine is getting hot and the antifreeze is boiling.

When the antifreeze boils, it's probably because your thermostat is stuck closed. That means the thermostat isn't letting water circulate through the radiator to get cooled. Thermostats are cheap...no more than $30 I'd say for most cars. Changing them is pretty easy too as they are usually right at the top of the engine. A mechanic may charge $100 to change it....but it's an easy job on most vehicles requiring just a couple sockets/socket wrench.

Head Gasket

STOP Using it NOW

hi.

water expands as it warms up, so spitting a little back out is normal.
what you must check for is a steady stream of bubbles coming out of the filler when the car is ticking over. a steady stream of small bubbles would suggest a blown head gasket.
if there are no bubbles in the cooling system, make sure the coolant is up the the maximum mark on the reservoir. then run the car for a day or two, keeping a check on the coolant levels. as long as the level does not go below the minimum marks, then you should be ok.

just to make sure... almost all cars need to run on a mix of water and antifreeze/summer coolant.
amount of antifreeze can vary, but 25% antifreeze will cover most situations..

hope this helps

Sounds like the water pump is leaking, the water pump is located on the front of the engine it is a common source of a leak like this.

If you squeeze the upper radiator hose and it feels like the coolant is running thru it, your pump is working. The system should bleed itself within a few minutes if you keep the radiator and reservoir full. If it continues to bubble, you have a blown head gasket. :-(

Let us know if you need more help.

With the engine cool open radiator cap. If the level is low you are losing coolant. Go for a 30/40 dollars, radiator compression test. Might be a bad radiator cap seal, water pump leak cylinder head gasket.
If the coolant level is in top, then there are many other reason.

A good possibility that you have a stuck water temperature thermostat blocking all flow of water into the radiator but the water in the engine block is boiling from not cirulating. I relatively inexpensive repair for the part and labor.

The water pump could also have had the impeller fail by coming loose from the pump drive shaft resulting in no water flow at all.

1. Thermostat
2. Water pump
3. Some one overserviced the reservoir at a "full service" gas station or during an over zealous oil change and service.

You should let the engine cool off, and then fill the radiator to the top. Start the engine, and then look from underneath the vehicle to see where exactly the fluid is coming from. Could be a hose, the radiator, or the water pump