OVERHEATING My 2005 cobalt keeps overheating even after cooling fan was replaced coolant leak fixed(ended up by passing heating system to fix leak, so no heat)(a/c is not working as well, refrigerant was added, I believe it may have too much now) Thermostat replaced Fuses and relays replaced or checked Coolant flushed out and new in What else could be the cause of overheating?

Change your thermostat. Ensure that your radiator fan is running at idle. See if your heat blows warm or not when the engine is warmed. if the heat is clod, then you have no water circulation in your engine. either the thermostat isnt opening up, or there is a blockage in your cooling system.

An overheated engine can be caused by anything that decreases the cooling system's ability to absorb, transport and dissipate heat; therefore engines can overheat for a variety of reasons. Let's take a look at some of the most common causes.
Cooling System Leaks
This is the primary cause of engine overheating. Possible leak points include hoses, the radiator, water pump, thermostat housing, heater core, head gasket, freeze plugs, automatic transmission oil cooler, cylinder heads and block. Perform a pressure test. A leak-free system should hold pressure for at least one minute.
Wrong Coolant Concentration
Be sure to use the coolant recommended by your vehicle's manufacturer. The wrong type of coolant and/or mixing the incorrect concentration of coolant and distilled water can also result in engine overheating. The best bet is to perform a complete flush and fill.
Bad Thermostat
A thermostat is a heat-sensitive valve that opens and closes in response to engine temperature. Heated engine coolant passes through to the radiator when the thermostat is in the open position. In the closed position, it prevents the flow of coolant to speed up the warming of a cold engine. When the thermostat gets stuck in the closed position, coolant stays in the engine and quickly becomes overheated, resulting in engine overheating.
Blocked Coolant Passageways
Rust, dirt and sediment can all block or greatly impede the flow of coolant through the cooling system. This can limit the system's ability to control engine temperature, which may result in higher operating temperatures and engine overheating. Once again, a flush and fill is recommended to remove debris.
Faulty Radiator
By passing through a series of tubes and fins, coolant temperature is reduced in the radiator. Leaks and clogging are some of the most common causes of radiator failure. Any disruption in the radiator's function can lead to elevated engine temperature and overheating.
Worn/Burst Hoses
A hose that contains visual cracks or holes, or has burst will result in leaks and disrupt the flow of engine coolant. This can result in overheating.
Bad Radiator Fan
A fan blows air across the radiator fins to assist in reducing the temperature of the coolant. A fan that wobbles, spins freely when the engine is off, or has broken shrouds will not be able to reduce the temperature to proper level, thus possibly resulting in engine overheating.
Loose or Broken Belt
A belt is often the driving link that turns the water pump at the correct speed for proper coolant flow through the cooling system. If a belt is loose or broken, it cannot maintain the proper speed, thus resulting in poor coolant flow and ultimately, engine overheating.
Faulty Water Pump
Known as the 'heart' of the cooling system, the water pump is responsible for pressurizing and propelling engine coolant through the cooling system. Any malfunction of the water pump, including eroded impeller vanes, seepage or wobble in the pump shaft, can prevent adequate coolant flow and result in engine overheating.

get it serviced

Overheating can seriously damage a car's engine if left unchecked. Although overheating simply means that a car's engine temperature exceeds normal operating temperatures, the causes of overheating are varied. What follows is a brief list of some of the most common causes of engine overheating.

Faulty Radiator
1. A car that overheats will often have a faulty radiator. A radiator is responsible for cooling hot engine coolant that picks up heat from inside a car's running engine. A radiator "radiates" the heat from engine coolant out into the outside air. A faulty radiator loses its "radiating" effects and allows engine coolant to become overheated, thus rendering it ineffective at adequately cooling and engine.
Faulty Water Pump
2. A faulty or malfunctioning water pump prevents adequate engine coolant flow and can cause a car to overheat. A water pump serves to pressurize and propel engine coolant throughout a car's engine and radiator to increase the heat-reducing capabilities of engine coolant. A faulty water pump loses its ability to adequately pump and propel engine coolant, and can cause a car to overheat.
Coolant System Leaks
3. A leaky engine coolant system reduces the level of circulating engine coolant, which increases engine temperature and leads to engine overheating. Radiators, water pumps, and coolant system hoses and seals--all of these coolant system parts can develop leaks, which can result in low coolant levels and engine overheating.
Faulty Thermostat
4. A car thermostat regulates the flow of engine coolant. A thermostat is a heat-sensitive valve that opens when a car engine reaches a set operating temperature and closes when a car engine is cold and warming up. If a thermostat gets stuck in the closed position, coolant will be prevented from reaching the engine, which will quickly lead to engine overheating and potential engine damage.
Low Engine Oil Level
5. Engine oil, in addition to lubricating an engine's internal parts, helps to keep engine operating temperatures reduced by eliminating friction within the engine. If engine oil levels are low, friction and heat build up inside an engine, a condition that causes increased engine operating temperatures and can lead to engine overheating.

Could be a faulty temperature sensor, at wost it's going to be a bad head gasket or intake manifold. Sorry for the bad news and hope that it's just a faulty temp sensor.

Thank you for using fixya and check your engine oil to make sure there is no coolant mixing in with your engine oil. Coolant is corrosive to your engine's internal bearings.

Sounds like you have a faulty head gasket or maybe a cracked head.This can cause overheating and the check engine light to come on.The code for the o2 sensor is probably caused by coolant getting into the exhaust system and coating the sensor.The coolant fan may work but it cannot remove enough heat from the rad to make the engine cool off.Try some engine coolant stop leak to see if it will help.This maybe only a temperary fix.Let me know if you need more.MOE

since this vehicle has a thermal clutch fan I'd start there

are ALL the hoses getting hot?

• upper rad hose
• lower rad hose
• heater hoses

does the overheating reduce when you turn on the heat at full speed

if there is a leak then of course you will get overheating from the engine..Be very careful as this can cause permanent damage to the head gasket and it will cost a lot more to fix..First try to stop this leak before you proceed further.

One of the most common reasons for a vehicle overheating is a stuck thermostat. It can stick or freeze in the closed position blocking the flow of coolant to your engine. The easiest way to check if your thermostat is not open is to feel the upper radiator hose. Once the engine warms up it should become warm. If it does not get hot the thermostat is probably not opening.

A second common cause of overheating is a leak in your vehicle's cooling system. If your vehicle is loosing coolant there will not be enough left in the vehicle to keep it cool. This is easy to diagnose as the radiator will be low on fluid and there will probably be a pool of coolant on the floor of your garage. Look for leaks in the most common places like around hoses and around the welds of your radiator. If you can not find the leak you might need to take it to a shop to have the cooling system pressure tested.

The third cause is a faulty water pump. The water pump is a vital part of your cooling system since it is responsible for circulating coolant through your engine. With a faulty water pump your vehicle will not run for more than a few minutes without overheating.

The fourth cause of overheating is a bad cooling fan. There are two types of fans, electric and mechanical. The electric fan should come on automatically once the vehicle reaches operating temperature or when the A/C is turned on. If it doesn't you should have it replaced. The mechanical fan will run all of the time but has a clutch which makes it turn faster when the engine heats up. With the car turned off the fan should not turn too easily especially when the vehicle is warm. You can also check for signs of leakage from the fan clutch. If you see any problems have it replaced.

The fifth cause of overheating I will talk about is a clogged radiator. Over time the radiator can accumulate deposits of rust and debris. This is especially true if radiator fluid has not been flushed on a regular basis. If you suspect a clogged radiator you should take it to a shop to have it professionally cleaned.

Those are some of the most common cause for vehicle overheating. Vehicle overheating can cause a great deal of damage to your vehicle. If you are experiencing trouble be sure to fix your vehicle or take it to a quality mechanic as soon as possible.

215 is not overheating. Does it keep getting hotter the faster you go? Does it cool off when slowing down or at idle? Does the Fan clutch or electric fan come on? When the engine is this hot.