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good stuff, good progress.

in this case it seems like the system is warning of actual malfunctions even if not a true over-temp/over-heat indication where there would be risk of permanent engine damage from heat.

so far it sounds like a case where the actual failure mode lacks a specific indication/error-message, so the system is issuing intermittent warnings about various/nearby failures as best as the programmers anticipated/designed/implemented.

in other words, it does not seem like a "false alarm" due to bad sensor hardware or software error or bayesian-decision-theory. It's probably at the risk of TMI already, but this should seal up the TMI label for this post: Bayesian decision theory guarantees that for any threshold-based yay/nay algorithmic decision, there will always be a nonzero false positive rate. and a nonzero false negative rate. the designer can trade-off between the two rates, selecting whether to prefer false negatives or false positives.
 

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Discussion Starter · #22 ·
Good news the car is out of paint shop for the repaint of the trunk deck paint blem and sensor/module will most likely get installed tomorrow then road testing etc, maybe home by the weekend. Then real world road testing by me on trip to CT to see my brother in laws hot new red loaded C7 and hopefully no mechanically negative events on the road trip for either chevrolet performance machine.
 

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I hate to resurrect this old thread, but I just had this issue last night. Roughly the same details: 2014, 75MPh+ on the highway, slowed to 35MPH then stopped at a light. About two minutes into the light the alarm went off and the temp gauge went to 11. The DIC then indicated it was turning off the A/C due to the overheating. I cranked on the heat and rolled down the windows. Once the light changed I pulled forward heading for the gas station across the street and the gauge went immediately back to normal (no slow cooling back to normal, just dropped exactly back to the normal location on the gauge). Checked under the car and saw no leaks or steam so I continued on. Stopped once on the way home and everything was fine. Got home and left the car running for five minutes with the A/C cranked but no alarm again.

SSLS3MD, if you're still around could you let me know what ended up fixing your issue? I see a few things in your previous post including the thermostat, radiator cap, a hose, and possibly a sensor. I want to be prepared with a list of items to check if I take it to the dealership.

Thanks in advance!
 

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Perhaps it's the Radiator Cap

I hate to resurrect this old thread, but I just had this issue last night. Roughly the same details: 2014, 75MPh+ on the highway, slowed to 35MPH then stopped at a light. About two minutes into the light the alarm went off and the temp gauge went to 11. The DIC then indicated it was turning off the A/C due to the overheating. I cranked on the heat and rolled down the windows. Once the light changed I pulled forward heading for the gas station across the street and the gauge went immediately back to normal (no slow cooling back to normal, just dropped exactly back to the normal location on the gauge). Checked under the car and saw no leaks or steam so I continued on. Stopped once on the way home and everything was fine. Got home and left the car running for five minutes with the A/C cranked but no alarm again.

SSLS3MD, if you're still around could you let me know what ended up fixing your issue? I see a few things in your previous post including the thermostat, radiator cap, a hose, and possibly a sensor. I want to be prepared with a list of items to check if I take it to the dealership.

Thanks in advance!
Try changing the radiator cap first; this is one of the cheapest and easiest to troubleshoot.

A way to troubleshoot a BAD Radiator Cap:
After the engine has been sitting overnight, but before starting the engine.
Before touching or changing the old radiator cap, and with the old cap on tight.
Look and feel if the upper radiator hose has collapsed, or feels empty, this will point towards the radiator cap being bad.

After changing the radiator cap, if the problem persists, try changing the thermostat, another cheap and easy thing to do yourself.

Tips:
Radiator Cap: There is not a good way to look at it and tell if it is bad.
Thermostat: Careful, the thermostat rubber gasket has an indicator on it. In other words, it fits into the thermostat housing in the SS engine block ONE WAY only.

Buy both OEM parts; there are many look-a-likes with different temp. ratings.

PS. My guess is on the radiator cap.
 

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Saturday I was at a car show and noticed that my upper radiator hose was collapsed.

I have no overheating or cooling issues, but I know the collapsed hose is not good.....

Not sure my certified preowned warranty will cover this....... Is it the hose or something else like the cap ?
 

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Saturday I was at a car show and noticed that my upper radiator hose was collapsed.

I have no overheating or cooling issues, but I know the collapsed hose is not good.....

Not sure my certified preowned warranty will cover this....... Is it the hose or something else like the cap ?
Here's a second opinion.:thumbsUp:
When the hoses are "flat" ie: sucked in ... it is because the vacuum valve in the radiator cap is bad. Could just be gunk; but a new cap is necessary since you can't effectively clean it. Do it sooner than later because the cooling system is not designed for vacuum.
 

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This is my follow-up post for anyone else that has a similar issue. Sorry it took so long, a guy at work just said "Man, I hate it when you see the same issue posted all over the place and no one ever answers..." and it reminded me to post an update.

My issue turned out to be a coolant temperature sensor that had gone bad. The dealer also said I was a little low on coolant. They replaced the sensor, filled the coolant, and added a dye to the system to help identify any leaks. I drove around for a few days and took it back for them to check it out. They found no leak and the sensor was reading proper voltage. They flushed the coolant system (I'm just over 60k miles) and sent me on my way. That was over a month ago and I've not had a repeat of the issue (knock on wood).

I hope this helps someone in the future!

JJ
 

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This Problem just happened to me. No issues (no bells, warnings, etc) of course i don't fixate on the temp gauge so i cant be for sure that it wasn't slowly overheating but did not notice it before i went into the bank, certainly no bells or warning came across display. Just 3 mile drive around town to bank. Come out start car as normal, within a minute the gauge was pegged over H, display says engine overheating - idle engine. I turn the car off, since i literally just started it, think about it for few minutes, and start it back up, everything is fine. This in 20 degree outside temps. Will check over later at home.
 

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If the coolant is full and the overflow bottle has never been empty and refilled incorrectly chalk it up to a glitch ... unless it reoccurs.
 

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For all of those who have had a concern similar to this.... We service many SS cars and I have as of yet to have an overheat concern on an SS in my service bays. Should the SS have an overheat (wether real or perceived as real) by the engine control module a diagnostic trouble code "P1258" will be stored. This is a type "A" trouble code meaning it will be stored at first failure and the check engine light will illuminate at that moment. The parameters for this to set is that the engine controller "sees" a temp of 270f for at least 10 seconds... Then you get the "ENGINE HOT"etc. type warnings. The powerplant in our cars is not a "usual suspect" in the overheat department even if you are a desert dweller. The SS engine temp gauge is poorly buffered (probably to eliminate not needed service department visits for minor fluctuations for over-zealous folks) and could "peg" with a "holy-crap" quickness. Sidebar on this the LS can also set a P0128 (Thermostat hanging open and the actual engine temperature is not plausible to the engine controller... In the P0128 case the engine controller assumes that the engine has been running for "X" period of time and the measured temperature is only "Y" so there may be an "unknown" temp and engine controller assumes this as an over-temperature condition as a form of redundant insurance so the controller may actually display a message that the engine is hot "SHUT OFF ENGINE", because it has deemed that engine temp is an "unknown". With the P0128 code AND the over-heat warning message the engine may ACTUALLY be BELOW operating temperature... A savvy tech would try to capture any "freeze-frame" data captured as I am sure there would be some, EVEN WITHOUT THE CHECK ENGINE LIGHT... Should the actual engine coolant temperature sensor display a low reading a sticking/stuck open thermostat is likely culprit...(P0128 Stored)... Should you have the P1258 stored I would be a bit more concerned... The DIY folks could probably throw one of those infra-red-laser-pointed thermometers at the radiator hoses to really see if there was an over heat OR a coolant temp sensor read problem to the engine controller... For all of our viewers....When these LS motors REALLY overheat you are gonna detect it with your nose...
 

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Well i went home and checked the overflow and radiator later that night. I added about a quart of antifreeze into radiator and overflow was empty. And i can honestly say i have never checked it in the 3 years of ownership.....Shame on me. I assume this was the issue. The next question is why was it low. Since i have no signs of any issues, leaks, smells, and I do check and change oil, that it is probably just evaporation?
 

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Well i went home and checked the overflow and radiator later that night. I added about a quart of antifreeze into radiator and overflow was empty. And i can honestly say i have never checked it in the 3 years of ownership.....Shame on me. I assume this was the issue. The next question is why was it low. Since i have no signs of any issues, leaks, smells, and I do check and change oil, that it is probably just evaporation?
I'd say if you don't smell or see a leak it may have been like that from the day you bought it. If you did have a problem and it took 3 years to seep a quart it won't show up looking at the oil dip stick. You could have an oil analysis done on the next oil change to find out if it's a problem.
 

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Well i went home and checked the overflow and radiator later that night. I added about a quart of antifreeze into radiator and overflow was empty. And i can honestly say i have never checked it in the 3 years of ownership.....Shame on me. I assume this was the issue. The next question is why was it low. Since i have no signs of any issues, leaks, smells, and I do check and change oil, that it is probably just evaporation?
I'll say it again ...

Put your thinking caps on guys ...

Overflow is next to radiator in a cramped hot engine compartment with a loose (open to atmosphere) cap.

Can we say evaporation ???

Each year I need to add 1 pint to keep it topped up. This is on a 3-4K a year car in the northeast.

Hotter climates will require more frequent topping off.

More usage will require more frequent topping off.

You are fine. Check it regularly when COLD. Only add 50/50 mix Dexcool.

No need to check the radiator if the overflow bottle stays full.
 

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THANKS CB! Simplicity at its best. Common Sense.
 
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Ok, add me to the list of those who get the “engine overheating” message followed by “idle engine” out of the blue. Open the hood, no overflow, steam or other indications there is actually an overheat issue. I will check the usual suspects noted in the thread but a little history:

  • car has almost 14k on it, it is a stock ‘16 manual
  • the cooling system was serviced/flushed in April this year at my dealer
  • I replaced the radiator cap with a new OEM ac/Delco at the same time

On a cruise last Saturday on the return (all highway driving) I got a random and very brief glimpse of a message on the DIC that I thought said something like “a/c off due to temperature” or “due to pressure”. It went away so quick I didn’t get a good read on it and there were no other messages/warnings. Engine temp gauge looked normal.

Today coming off highway after about a mile on regular street, no prolonged stops, or idling and it is cool out (70 degrees). The “engine overheating” message comes up with rapid chime, along with “idle engine”. A/c was off entire 15 minute drive. I pull into a parking lot, open hood and everything looks, smells, and feels ok. other than the fan running high. The temp gauge is pegged high, but will quickly (as in nearly instantaneously) drop to about 80% of full right then and peg again. Let it sit idling for a few minutes then shut off and sit another minute or so. Fan continued to run while engine was off. Restarted, immediately same engine overheating message and temp pegged.

I’m thinking sensor-related rather than actual cooling issue, but it looks like it will be about a week before the dealer can get to it.


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So twice now after the overheating issue (2d time I confirmed with DashCmd that coolant temp was above 250 degrees indicated) after letting the car sit for a while, when I released the radiator cap (slowly) there was a definite thunk and sound of coolant moving from the overflow tank side of the bay. This was with a new OEM ac/Delco cap RC115/13502509 bought from Amazon that has been on the car for about 6 weeks.

I’m going to try the original cap that came on the car (they do look the same) but does the above sound like a likely cap issue rather than something else?


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Ok, add me to the list of those who get the “engine overheating” message followed by “idle engine” out of the blue. Open the hood, no overflow, steam or other indications there is actually an overheat issue. I will check the usual suspects noted in the thread but a little history:

  • car has almost 14k on it, it is a stock ‘16 manual
  • the cooling system was serviced/flushed in April this year at my dealer
  • I replaced the radiator cap with a new OEM ac/Delco at the same time

On a cruise last Saturday on the return (all highway driving) I got a random and very brief glimpse of a message on the DIC that I thought said something like “a/c off due to temperature” or “due to pressure”. It went away so quick I didn’t get a good read on it and there were no other messages/warnings. Engine temp gauge looked normal.

Today coming off highway after about a mile on regular street, no prolonged stops, or idling and it is cool out (70 degrees). The “engine overheating” message comes up with rapid chime, along with “idle engine”. A/c was off entire 15 minute drive. I pull into a parking lot, open hood and everything looks, smells, and feels ok. other than the fan running high. The temp gauge is pegged high, but will quickly (as in nearly instantaneously) drop to about 80% of full right then and peg again. Let it sit idling for a few minutes then shut off and sit another minute or so. Fan continued to run while engine was off. Restarted, immediately same engine overheating message and temp pegged.

I’m thinking sensor-related rather than actual cooling issue, but it looks like it will be about a week before the dealer can get to it.


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Did you try and pull any codes from it?
 

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smart move to go back to cap that had no problem.......that would be a SOB wouldn't it ? (happened to my Miata) But....why would the coolant temp actually be over 250 from a slightly defective cap.? thermostat stuck shut. water pump falling apart. Are you sure the coolant temp is alarmingly high?? The fans on hi means the sensor is saying so. What would be nice to have happen is to have the coolant tell you its high after just being started (from cold) for a short time, where its impossible to get that hot, that quick.....
 

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I have no real answer on how the cap may play here, I just know it has been identified in other posts as a possible culprit for cooling issues, though I don’t really know the role a properly functioning cap plays in coolant flow through the system.

It’s an easy try, but I would agree that the most likely culprit at this point may be a sticking thermostat or sensor issue. If it overheats again I’ll put a temp gun on the coolant outflow hose and see what it says…


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