what could make a 2004 chevy cav run hot it only run hot some time?

[DAMIEN H]

when the low coolant light comes on its about to run hot after you open the coolant and let the steam out and add water it b ok

[webjnke1]

if you keep only adding water, you probably have it too watered down. which makes it heat up and boil away faster.

[readupmore.]

First, never open a radiator cap when it is hot. The cap maintains a pressurized system. Removing the cap lowers the pressure which can result in instant boiling with scalding steam. A 50/50 mixture of water and antifreeze boils at a higher temperature than water and can carry the heat from the engine to the radiator more efficiently than water. If you add plain water in an emergency you have to add antifreeze in an equal amount. There is usually some extra space in the fill bottle to add some straight antifreeze. Install a new radiator cap and thermostat then find any leaks and fix them. You may also want to have the radiator flushed. Carry a 50/50 mixture of antifreeze and water with you. I think you can actually buy it that way. Don't put antifreeze in any unapproved container. If it spills on the ground it has a sweet taste that animals like and it will kill them it they consume it.

[Texas]

The most common cause of this that I have observed is a "stuck thermostat".

Thermostat is typically around where the water pump is. You can find more specific info in your owners manual or service manual, or buy or borrow a service manual at a local public library or auto parts shop.

Thermostat normally holds closed when the engine is cold to prevent water circulating, and then when it gets hot, the metal bends open. If something is broken it may stay stuck closed when the engine is warm, so then the result would be your engine overheats if you drive for longer than 15-20 minutes at a time, and your interim workaround might be to just drive short distances and add water every other gas station you pass.

It could also be a bad water pump. Try replacing the thermostat first, and if that doesn't solve it, also the water pump. And of course check the belt to the water pump and make sure it is in good condition, of course a broken or slipping water pump belt can also prevent proper cooling.

And some other possible causes are plugged or cracked radiator hoses, or leaky or plugged radiator. Replacing radiator hoses might just be a good idea if they look cracked or abraded.