Plugged heater core maybe.
Maybe the thermostat. Coolant keeps your engine cool under duress. If the thermostat is stuck open, the engine is staying too cool. Your heat is run off of your engine temperature.
If your radiator isnt leaking and car is having a over heating problem and coolant spewing out. Chances are your thermostat needs replaced. possible the radiator needs to be flushed. But more likley its thermostat
Fill it up with coolant. If it gets low again I'm guessing you have a hole in your radiator. Replace it.
Here are a few possibilities:engine cooling fan not working.low radiator fluid.plugged radiator fins (not enough airflow through radiator).blocked or collapsed coolant hose.faulty engine thermostat.blown head or intake gasket.vehicle cargo or towing capacity is exceeded.
Check; coolant, fan, fan clutch and fan clutch solenoid, blocked or partially blocked lines and coolant gallery.
I had this problem ....Head Gasket or radiator cap
From easiest to hardest: Does radiator have enough coolant? Is the fan working? Could be a bad thermostat. Water pump (there is a small hole in the bottom of the water pump. If there is water dripping out of the "weep" hole, then the water pump is bad). Could be a blown head gasket. (Is there any water in the oil or does the coolant in the radiator have a fuel smell?
You could possibly have a circulation problem, or a over heating problem. Need more info.
The Engine Coolant Temperature in the Engine is higher than it should be. Check your radiator coolant level - also your radiator may be clogged or thermostat may be stuck.
Build up in the radiator system or a plug can cause this. Do a radiator flush (or have a professional do it if you're not interested but it's fairly easy if you read an online HOWTO) to remove the grime and refill with fresh coolant. This solved the problem in my 2003. Check the low coolant level sensor and replace if defective. It is in the side of the radiator.
sounds like blockage in the cooling system. See if you are not low on coolant in the radiator. Just because your reserve tank has coo;ant does not mean that you have enough coolant in the radiator. If you have low coolant in the radiator, it will blow cold. It can happen abruptly. If you are low on coolant in the radiator and not in your reserve tank you will need to find out why the system is not pulling coolant out of the reserve tank.
If it is an automatic transmission, the cooler in the radiator is most likely leaking into the coolant system.
Your radiator cap is made of metal and rubber. The metal and rubber are reacting to the rust in your radiator. Rust and oxidation in your radiator will deteriorate the cap at an accelerated rate. I suggest flushing the cooling system and replacing the coolant and cap. If it persists after that you might have a heat problem that is cooking the rubber right off the radiator cap. If this is the case you should check your thermostat and heating Coil.