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Discussion Starter · #1 ·
Was having the dreaded === F for coolant temp reading all it was a bad ground just above the temp sender on the head check your grounds
 

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The temperature reading displaying ——— is often caused by a bad thermostat. The computer on these cars is programmed to have the temperature rate of change happen in a certain amount of time. If the temperature doesn’t rise fast enough, as when a thermostat is stuck open, it’ll show ———. I’m not quite sure if the same thing happens when it’s stuck closed or not as the temperature may rise but not flow coolant into the area where the sensor is located. Which is right beside the thermostat. Stuck closed would also cause an overheating issue. Occasionally it is a sensor causing the issue. But I have fixed more or this particular problem with a new thermostat.

I would suggest by first making sure the coolant is full in the reservoir. If it’s not empty or extremely low, it may be time for a thermostat. I highly recommend you used a quality thermostat and don’t cheap out by purchasing the cheapest one available. Many times the cheap ones either don’t open at the correct rate or the opening temperature is slightly off and can also cause the ——— to display again or other issues.

I personally used a Stant OE type thermostat. It wasn’t the most expensive, but wasn’t a cheap piece of crap. Most thermostats available now days are either made in China or Israel from what I’ve purchased for various customers vehicles. Stay away from the Motorad Fail Safe thermostat, they seem to always get stuck open. Their premium ones are ok.

I also flushed the cooling system out completely and filled the system with Prestone yellow/green coolant to replace the orange Dexcool. I have had many instances where I’ve worked on GM vehicles and found the Dexcool with sludge. I assume it’s not just the Dexcool alone causing problems, but I will not used the stuff in my personal vehicles. I've used Prestone coolant for years and had no adverse problems in the cooling systems I’ve used it in. Just my preference. And the stuff isn’t really very expensive. Also can be found at most auto parts or grocery stores, so easy to access.
 

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Discussion Starter · #3 ·
The temperature reading displaying ——— is often caused by a bad thermostat. The computer on these cars is programmed to have the temperature rate of change happen in a certain amount of time. If the temperature doesn’t rise fast enough, as when a thermostat is stuck open, it’ll show ———. I’m not quite sure if the same thing happens when it’s stuck closed or not as the temperature may rise but not flow coolant into the area where the sensor is located. Which is right beside the thermostat. Stuck closed would also cause an overheating issue. Occasionally it is a sensor causing the issue. But I have fixed more or this particular problem with a new thermostat.

I would suggest by first making sure the coolant is full in the reservoir. If it’s not empty or extremely low, it may be time for a thermostat. I highly recommend you used a quality thermostat and don’t cheap out by purchasing the cheapest one available. Many times the cheap ones either don’t open at the correct rate or the opening temperature is slightly off and can also cause the ——— to display again or other issues.

I personally used a Stant OE type thermostat. It wasn’t the most expensive, but wasn’t a cheap piece of crap. Most thermostats available now days are either made in China or Israel from what I’ve purchased for various customers vehicles. Stay away from the Motorad Fail Safe thermostat, they seem to always get stuck open. Their premium ones are ok.

I also flushed the cooling system out completely and filled the system with Prestone yellow/green coolant to replace the orange Dexcool. I have had many instances where I’ve worked on GM vehicles and found the Dexcool with sludge. I assume it’s not just the Dexcool alone causing problems, but I will not used the stuff in my personal vehicles. I've used Prestone coolant for years and had no adverse problems in the cooling systems I’ve used it in. Just my preference. And the stuff isn’t really very expensive. Also can be found at most auto parts or grocery stores, so easy to access.

Sorry should have started at the beginning already replaced thermostat and temp sensor thermostat because it was running hotter than the normal 187 ,put it back together got the ———F then changed temp sensor no joy read one thread that said check ground on Steering column saw the ground I described in first post will have to re-terminate as 4 wires in it were just crimped will solder it
 

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While you’re under the hood, make sure the wire loom hasn’t worn away on the wiring harness that runs next to the oil filter housing. The sharp edge on the engine will cut right through the wires and can cause many issues. They sell the wire loom at most auto parts stores. I still need to find the larger size for the larger bundles of wire.
 

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Discussion Starter · #5 ·
While you’re under the hood, make sure the wire loom hasn’t worn away on the wiring harness that runs next to the oil filter housing. The sharp edge on the engine will cut right through the wires and can cause many issues. They sell the wire loom at most auto parts stores. I still need to find the larger size for the larger bundles of wire.
try a piece of hose split it then a couple of zip ties
 

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I’ve had to do that before. I should be able to find the wire loom. But that would be a good idea for the wire bundle that scrapes the oil filter housing.
 

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Discussion Starter · #8 ·
Hi,
Can anyone tell me the location of the temp sensor and thermostat in a 2010 cobalt??
Follow the driver side hose from radiator to the thermostat housing temp sensor is right there close Look for a brass fitting on back side of head 17 or 19 mm hex
 
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