Is a head gastic major work? Outside or inside the engine?

Yes, you are running hot from leaking all your coolant out. No one can tell you where it is leaking without looking at it. Could be a hose leaking, the radiator, a bad head gasket or intake gasket, the water pump...if coolant is leaking from the front of the engine, that could be the water pump or radiator hose or a water pump gasket. Pretty common for the water pump to leak when it is worn out, that's how you know when to change it.

When you fill the radiator and overflow tank back up to full, does the engine still run hot? If it does, I would not advise running it-have a shop diagnose it before more serious damage occurs. Head gasket repairs can get very expensive-that is the danger you are facing, and if the head gasket has already gone bad from overheating, continued running of the engine can cause you to have to replace the engine. Overheating is a major cause of early engine failure.

Try to determine where the leak is, from where it drips off the engine. The coolant constantly circulates from the engine to the radiator and back into the engine. The heater hoses circulate coolant from the engine to the heater core in the heater case and back into the engine. Besides the overflow tank, these are the only places coolant would be on the car. The engine can leak coolant from a lot of places, but if leaking to the outside, you should be able to spot where it is coming from. Good luck.

Sounds like your heater core is bad and is leaking. Do you smell coolant inside the car? The reason your temp goes up and down is there is a air pocket developing for the missing coolant and its struggles to keep the flow through the system properly

If the water is coming from your overflow tank or radiator cap, replace them. The seals may have went bad. If the water is coming from a hose connection in the engine compartment, fix the connection. Depending on where/what is leaking it could be as simple as tightening a hose clamp and/or replacing a hose.

In back of the head theres is a plastic housing which holds the coolant temperature sensor and a few hoses. this platic housing is know for leaking. hope this helps good luck.

You probably didn't sustain any major damage. You should be concerned about the loss of coolant. If there is no evidence of a leak where you park then it;s possible you could have a leak that only happens with the engine running. Being a late model GM car, it uses a coolant called DexCool. It is pink in color and is known to cause deterioration of certain gasket materials. In particular, the upper intake plenum gasket. These leaks are difficult to find. With the engine running, use a bright flashlight and look for coolant puddling around the edges of the intake plenum. Also check your radiator and heater hoses for pinhole leaks that could open up when the coolant gets hot. Be sure and keep a close eye on your coolant level until you find out if you have a leak.

thermastat problem? Antifreeze not circulating properly? Radiator needs flushing?

I don't currently have access to step by step instructions for your Kia Sorento, but I would imagine that it takes a standard tool ratcheting tool set to unscrew the bolts for the shroud, and lift any fans out of the way. Then, the radiator hold down hardware can be removed and the radiator should be disconnected fromt he cooling system (via the hoses) and then you can pull it out. It does not weigh much.

Installation is the reverse of the removal.
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recalls for engine follow:

Gasoline Engines
2004 KIA SORENTO

03/01/2009 KIA REMANUFACTURED ENGINE PROGRAM 01/01/2004 CYLINDER BLOCK DAMAGE - HEAD GASKET LEAK - POOR RUNNING OR HARD START, EXCESSIVE WHITE SMOKE AND/OR COOLANT SMELL FROM EXHAUST, MISFIRE DTC - REVISED 06/01/2005 LOCKNUT RE-USE PROHIBITED 07/30/2007 CRANKSHAFT PULLEY BOLT REPLACEMENT

2004 kia sorento, thermostat replaced, all belts, water pump. now there is a coolant leak again, cannot tell where it is coming from. Leaks fairly quickly and overheats within 20 mins. Heat is not working when coolant is not full....could it be the coolant resevoir? head gasket??

There should be hoses (2) running from the engine to the cabin heater and back. These would be at the back of the hood area, but down low. Watch your coolant level. If it is dropping then you have a problem. It could be a head gasket also that is spraying out the back of the engine. You just need to find the leak and fix it or have it fixed

Good luck and hope this helps you

first check the exhaust... if it is white you have a blown head gasket.... next issue may be a stuck thermostat next place to look is the water pump, there is a "weep" hole on the casting, if that is leaking you will need to replace the water pump