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Normal coolant temp, thermostats, and AC off due to high engine temp

68110 Views 12 Replies 9 Participants Last post by  my2010cruze
Late last week on the way home I suddenly got the message "AC off due to high engine temp" message, and the temp gauge starting spiking. I had just checked the coolant level the day before and it was fine, but turned the heat and fan on high and pulled over as quick as I could and checked the level. It was low. I added coolant, as then started up the Cruze, and checked the temperature. The gauge went back down so I started driving again.

I kept monitoring the temperature display, as I have the digital readout, my Cruze being a 2012. Driving temperature was now running low, in the 150 degree range and it wouldn't go any higher.

What I think happened is the thermostat got stuck closed, blew off a bunch of coolant out of the coolant reservoir, and then somehow the thermostat got stuck open. Whether this was by accident, or by design to protect the engine, I don't know.

I bought a new thermostat and replaced it over the weekend. Today, I monitored the coolant temp all day, driving about 200 miles for work, and noticed something different. Coolant level is still fine, but my normal "high" coolant temperature is now 195 to 200 degrees. If I really push it, I can get it as high as 207. Normal operating temperature used to be in the 210 to 220 degree range.

I researched the thermostat part numbers, and as far as I can tell, the part number has changed. It used to be part number 55579010, and now it is 55593034. What is going on here? As I understood it, the thermostat is electronically controlled, so why did my "normal" coolant temperature change?
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Discussion Starter · #2 ·
No one, huh?

Ok, chew on this...

Why did the thermostat part number change? I haven't heard of any specific issues with thermostats on the 1.4L Cruze. Why would they lower the normal operating temperature of the thermostat? There must be something different about it, resistance-wise or electronically. Is there a microchip on the sensor in the thermostat?

Perhaps they decided the higher operating temperature was causing an issue, either with the longevity of plastic parts like the water outlet, or that the higher temperature was causing coolant boil off and/or odor.

Or am I just blowing smoke, and there is something else going on?
 

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Discussion Starter · #5 ·
When cruising at a steady rate my 2012 runs 217-223F, always has. Floor the gas or max out the load on a hill and the temperature drops to 190-210F range.
That's what mine used to do. Now my normal cruising temp is 190 to 200 degrees.
 

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Discussion Starter · #10 ·
I should have updated this thread.

After a week or so, operating temperatures returned to their normal levels. There must have still been some air in the system, even after a couple days and a couple hundred miles of driving.
 
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