* Remove heat from the engine: This is the primary function. Failures here are the most common cause of overheating.
* Low coolant level: The most obvious and easiest to check. Look for leaks (look under the car for puddles, check hoses and the radiator for cracks or damage). A leak can be slow and subtle, leading to gradual depletion. Check the coolant reservoir (usually a translucent plastic tank) regularly.
* Faulty water pump: The water pump circulates the coolant. A failing pump won't circulate properly, leading to overheating. Listen for unusual noises (whining or grinding) coming from the pump area.
* Clogged radiator: The radiator dissipates heat. If it's clogged with debris, dirt, or rust, it can't cool the coolant effectively. This often requires flushing the system or radiator replacement.
* Faulty thermostat: The thermostat regulates coolant flow. If it's stuck closed, coolant won't circulate properly. If it's stuck open, the engine might take longer to warm up but shouldn't overheat (unless combined with other problems).
* Failing radiator fan: The radiator fan helps cool the radiator, especially at low speeds or idle. If it's not working, the radiator can't dissipate heat effectively. Check the fan's operation directly – does it come on when the engine is hot? Also check the fan relay and its wiring.
* Blocked airflow to radiator: Anything obstructing the radiator (leaves, debris, etc.) can prevent proper cooling.
* Dissipate heat to the environment: The cooling system relies on effective heat transfer to the outside air.
* Failing cooling fan clutch: Similar to the radiator fan, this clutch engages the fan at higher temperatures. If it's faulty, the fan might not spin fast enough.
* Other less common causes:
* Head gasket failure: This is a more serious problem where coolant leaks into the combustion chamber or the oil. You'll likely see white smoke from the exhaust, milky oil, or low coolant level despite no visible leaks.
* Warped cylinder head: This prevents proper sealing and can lead to overheating.
* Low compression: Insufficient engine compression can lead to overheating.
Troubleshooting Steps:
1. Check coolant level: This is the absolute first thing to do.
2. Inspect hoses and radiator for leaks: Look for any signs of damage.
3. Check the thermostat: Make sure it opens and closes correctly.
4. Test the radiator fan: See if it turns on when the engine is hot.
5. Feel the upper and lower radiator hoses: If the upper hose is hot but the lower hose is cool, the thermostat is likely stuck closed.
6. Listen for unusual noises from the water pump: Whining or grinding can indicate a failing pump.
Important Note: Overheating can cause serious engine damage. If your Cadillac STS is overheating, do not continue driving it. Have it towed to a mechanic for proper diagnosis and repair. Attempting DIY repairs without the necessary knowledge can worsen the problem.
