Coolant temp too low?
Instructor
Joined: Mar 2018
Posts: 233
Likes: 70
I had the same problem in my 2014 M7 Z51 (the yellow bars would come back ON on the highway after the engine had warmed up in the city and the yellow bars had extinguished), and it was NOT the OEM thermostat nor its OEM replacement, both of which tested fine.
In my case, it was a very small leak from an aftermarket larger radiator from the PO. Once I replaced the radiator with a stock, new radiator (only change), all such problems went away.
In my case, it was a very small leak from an aftermarket larger radiator from the PO. Once I replaced the radiator with a stock, new radiator (only change), all such problems went away.
Moderator emeritus
Joined: Jun 2001
Posts: 18,599
Likes: 3,954
From: Jacksonville Florida BWO Dayton, Cincinnati, Bloomsbury NJ, Cincinnati
2015 C7 of the Year Finalist
I had the same problem in my 2014 M7 Z51 (the yellow bars would come back ON on the highway after the engine had warmed up in the city and the yellow bars had extinguished), and it was NOT the OEM thermostat nor its OEM replacement, both of which tested fine.
In my case, it was a very small leak from an aftermarket larger radiator from the PO. Once I replaced the radiator with a stock, new radiator (only change), all such problems went away.
In my case, it was a very small leak from an aftermarket larger radiator from the PO. Once I replaced the radiator with a stock, new radiator (only change), all such problems went away.
Elmer
Instructor
Joined: Mar 2018
Posts: 233
Likes: 70
Hmm, ok, a radiator leak made the car show cold temperatures. Sorry, I'm at a loss here. Coolant loss would not allow the car to get colder or cooler. Coolant loss would have the engine go hot and lock up the engine. Sorry to have to ask this, but was your problem overheating or did the tach bars show up because the coolant temp went down?
Elmer
Elmer
I had a consistent, "Car runs too cold at highway speeds" problem, over several months, from the day I bought it. Eventually I fixed it by replacing the (3x larger) aftermarket radiator (that had a small leak) with a stock radiator. Prior tests of the thermostat all showed that the thermostat was functioning properly. No other components were changed.
It seemed to me like the larger, "race" radiator's cooling capacity was simply overwhelming the system as a whole, despite the fact that there is a thermostat in there that ought to regulate things properly.
Team Owner
Joined: Aug 2006
Posts: 25,105
Likes: 3,156
C6 of Year Finalist (appearance mods) 2019
I did not have overheating problems (apart from the known 2014 radiator fan has a bug).
I had a consistent, "Car runs too cold at highway speeds" problem, over several months, from the day I bought it. Eventually I fixed it by replacing the (3x larger) aftermarket radiator (that had a small leak) with a stock radiator. Prior tests of the thermostat all showed that the thermostat was functioning properly. No other components were changed.
It seemed to me like the larger, "race" radiator's cooling capacity was simply overwhelming the system as a whole, despite the fact that there is a thermostat in there that ought to regulate things properly.
I had a consistent, "Car runs too cold at highway speeds" problem, over several months, from the day I bought it. Eventually I fixed it by replacing the (3x larger) aftermarket radiator (that had a small leak) with a stock radiator. Prior tests of the thermostat all showed that the thermostat was functioning properly. No other components were changed.
It seemed to me like the larger, "race" radiator's cooling capacity was simply overwhelming the system as a whole, despite the fact that there is a thermostat in there that ought to regulate things properly.
Moderator emeritus
Joined: Jun 2001
Posts: 18,599
Likes: 3,954
From: Jacksonville Florida BWO Dayton, Cincinnati, Bloomsbury NJ, Cincinnati
2015 C7 of the Year Finalist
I did not have overheating problems (apart from the known 2014 radiator fan has a bug).
I had a consistent, "Car runs too cold at highway speeds" problem, over several months, from the day I bought it. Eventually I fixed it by replacing the (3x larger) aftermarket radiator (that had a small leak) with a stock radiator. Prior tests of the thermostat all showed that the thermostat was functioning properly. No other components were changed.
It seemed to me like the larger, "race" radiator's cooling capacity was simply overwhelming the system as a whole, despite the fact that there is a thermostat in there that ought to regulate things properly.
I had a consistent, "Car runs too cold at highway speeds" problem, over several months, from the day I bought it. Eventually I fixed it by replacing the (3x larger) aftermarket radiator (that had a small leak) with a stock radiator. Prior tests of the thermostat all showed that the thermostat was functioning properly. No other components were changed.
It seemed to me like the larger, "race" radiator's cooling capacity was simply overwhelming the system as a whole, despite the fact that there is a thermostat in there that ought to regulate things properly.
Ok, I still have a problem with my logic on this.
First, what temperature was the thermostat? I'm guessing it might not have been stock and if that is the case, the "cold" signals on the tach were from a t-stat that was for racing (150° or 160°) and not normal driving.
Second, even with the huge radiator, an OEM t-stat (195°) would keep the car warm enough so the tach "cold" bars would not reappear. The t-stat would open, but not fully, to control the temp.
Third, a leaking radiator would not cause the engine to "overcool". Low coolant will overheat an engine, so for a cold engine condition, it should not be in the conversation at all except it definitely was cause to replace the radiator.
Elmer
Melting Slicks
Joined: Mar 2013
Posts: 3,104
Likes: 626
From: Baton Rouge LA
Same year GS here, stock tstat, similar problem. Last summer I noticed coolant temps were running 180-185° and was keeping an eye on the gauge during that period. Drove it yesterday in coolish (for us in S. LA) 50° temps and didn't take notice as I should have. Mine is not stuck open, as this summer it climbed up predictably and peaked at the temp mentioned, but should stop higher, around 195°. Will watch more closely in next drives.
Instructor
Joined: Mar 2018
Posts: 233
Likes: 70
Ok, I still have a problem with my logic on this.
First, what temperature was the thermostat? I'm guessing it might not have been stock and if that is the case, the "cold" signals on the tach were from a t-stat that was for racing (150° or 160°) and not normal driving.
Second, even with the huge radiator, an OEM t-stat (195°) would keep the car warm enough so the tach "cold" bars would not reappear. The t-stat would open, but not fully, to control the temp.
Third, a leaking radiator would not cause the engine to "overcool". Low coolant will overheat an engine, so for a cold engine condition, it should not be in the conversation at all except it definitely was cause to replace the radiator.
Elmer
First, what temperature was the thermostat? I'm guessing it might not have been stock and if that is the case, the "cold" signals on the tach were from a t-stat that was for racing (150° or 160°) and not normal driving.
Second, even with the huge radiator, an OEM t-stat (195°) would keep the car warm enough so the tach "cold" bars would not reappear. The t-stat would open, but not fully, to control the temp.
Third, a leaking radiator would not cause the engine to "overcool". Low coolant will overheat an engine, so for a cold engine condition, it should not be in the conversation at all except it definitely was cause to replace the radiator.
Elmer
All was fixed solely by replacing the radiator with a stock radiator.
My first post on the issue: https://www.corvetteforum.com/forums...post1598754047
And my thread on solving it (with lots of pics and data): https://www.corvetteforum.com/forums...post1598769848
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Racer
Joined: Sep 2021
Posts: 267
Likes: 102
From: Prosper, TX
When my builder built my engine with the Magnuson 2650 supercharger one of the other things they did was replace the stock thermostat with a 160 degree thermostat. I’m not a builder so I don’t know why but I assume it’s to keep the engine running cooler.
I have the same issue described by other posters where my engine according to the tach gage won’t warm up or it does and then drops back down where those yellow bars will show up for a while.
my builder said that is normal and to not worry about it.
I have the same issue described by other posters where my engine according to the tach gage won’t warm up or it does and then drops back down where those yellow bars will show up for a while.
my builder said that is normal and to not worry about it.
Moderator emeritus
Joined: Jun 2001
Posts: 18,599
Likes: 3,954
From: Jacksonville Florida BWO Dayton, Cincinnati, Bloomsbury NJ, Cincinnati
2015 C7 of the Year Finalist
When my builder built my engine with the Magnuson 2650 supercharger one of the other things they did was replace the stock thermostat with a 160 degree thermostat. I’m not a builder so I don’t know why but I assume it’s to keep the engine running cooler.
I have the same issue described by other posters where my engine according to the tach gage won’t warm up or it does and then drops back down where those yellow bars will show up for a while.
my builder said that is normal and to not worry about it.
I have the same issue described by other posters where my engine according to the tach gage won’t warm up or it does and then drops back down where those yellow bars will show up for a while.
my builder said that is normal and to not worry about it.
It's probably true, ignoring it is fine BUT, I would twitch a little if the tach lights came back on after warming up the car.
Elmer
Instructor
Joined: Dec 2021
Posts: 118
Likes: 42
I bet my 2019 has this issue too. I just bought it a month ago and always noticed it takes forever to get warmed up. It will eventually get up to temps but only after 15mins of idle warm up and 3-4 miles of easy driving. If I park and go into a store for a bit the bars will be back when I restart it. I noticed the other day it took forever to warm up on a 50 degree day. I had to drive my Nissan Titan somewhere that day and it warmed up in 5 mins.