Low Engine Temperature

[cgraves817]

2016 Tahoe LTZ
I have noticed for awhile engine temperature won't raise above 170 degrees. Didn't bother me till it got cold outside. With the engine temperature so low I get only lukewarm heat.
I also occasionally get the annoying zero temp reading and the engine fans run. I have already replaced the temp sensor.
Thinking thermostat now????

 

[L8T BURB]

I realize this will sound odd, but all you need to do is replace the thermostat with a GM Genuine part. The issue is that the thermostat gets stuck partially open and will not allow the engine to consistently get to full operating temperature. Once you replace the thermostat, you'll need maybe a half gallon or so of Dexcool, as you'll lose a little when you remove the old thermostat. Once the repair is done, use a pocket scanner or similar to clear any stored engine codes. Typically this failure will store a code of "coolant temp below threshold". Sometimes it won't actually illuminate the check engine light, but it will store the code. The engine fans running and temp gauge dropping to zero is due to this stored code causing the system to run in fail safe mode. Without clearing the stored code, the symptoms may persist for a short period after the thermostat replacement. Scanning and clearing the codes when replacing the thermostat is the sure bet for a successful repair.

Funny thing, people on this forum are still convinced that this is a temp sensor issue. I bet $100 if you replace the thermostat and put your OLD temp sensor back in, you'll be good to go. The new temp sensor is fine of course, but it's not the root cause of the problem you're having.

 

[strutaeng]

You can always remove your thermostat and dunk it in an old pot of boiling water and see it open. It's a slow action though.

However, if it's not warming up, I think that means that it's open all the time, no? Or maybe partially open as @L8T BURB suggested. When it's running at operation temperature, does the coolant hose feel warm?

I had a thermostat fail once on my 99 Silverado and in the winter, there was simply no real heat. A new thermostat is easy to replace and inexpensive. I would just get a new GM Genuine and pop it in there.

 

[cgraves817]

I realize this will sound odd, but all you need to do is replace the thermostat with a GM Genuine part. The issue is that the thermostat gets stuck partially open and will not allow the engine to consistently get to full operating temperature. Once you replace the thermostat, you'll need maybe a half gallon or so of Dexcool, as you'll lose a little when you remove the old thermostat. Once the repair is done, use a pocket scanner or similar to clear any stored engine codes. Typically this failure will store a code of "coolant temp below threshold". Sometimes it won't actually illuminate the check engine light, but it will store the code. The engine fans running and temp gauge dropping to zero is due to this stored code causing the system to run in fail safe mode. Without clearing the stored code, the symptoms may persist for a short period after the thermostat replacement. Scanning and clearing the codes when replacing the thermostat is the sure bet for a successful repair.

Funny thing, people on this forum are still convinced that this is a temp sensor issue. I bet $100 if you replace the thermostat and put your OLD temp sensor back in, you'll be good to go. The new temp sensor is fine of course, but it's not the root cause of the problem you're having.

Thank you!!! I will replace thermostat!

 

[Tonyv__]

Thank you!!! I will replace thermostat!

I’m just here to say you’re on the right track. I’m 99% sure it’s thermostat. I had the same exact problem on my Yukon and another member on her just went through it too.

You may even have a check engine code stored that you don’t know about.

 

[Marky Dissod]

The truck('s engine) burns more gas when it’s not up to temp because it wants to warm up. Thus your engine will run rich.

Running rich cools combustions ...

 

[Tonyv__]

Running rich cools combustions ...

Hmmm then I’ll edit my statement so I’m not sharing false information.

so I swore I read somewhere that when the vehicle is so under temperature for long periods of time that the engine burns more fuel to warm up. I thought that was running rich.

When my Yukon wouldn’t get up to temp. I got a catalytic code eventually. (I don’t remember if it was rich or lean) but researching that code lead me to understanding that my temp on the Yukon was not normal. After replacing the Tstat. My temp shot up to the proper 200ish range and the permanent cat code cleared itself.



So I’m still learning everyday but I thought it made sense that burning more gas would heat up and run rich.

 

[Doubeleive]

2 different issue's in the above statement, stuck thermostat and bad temp sensor in general can cause 2 different issue's
a stuck open thermostat results in low temps (that is correct), same if there is a stuck closed thermostat (high temps and cel)
a non op temp sensor can result in a default state that results in a 0 gauge temp reading and makes the fans run high speed and ac to be turned off because it cannot get a correct temp reading so it assumes the engine may be overheating. or it might think it is not heating but the air temperature and oil temperature readings are conflicting......
this "can" happen from a bad thermostat also as it causes a default state, but it could be the temp sensor as well
when you have a mixed bag, some troubleshooting should be performed such as using a temperature reader on the coolant to confirm or testing the temperature sensor.
or shotgun it with both the sensor and thermostat and in some cases that doesn't fix it either. some say then it could be a bad battery, bad harness connector, bad wiring, bad ecm.
apparently there is no clear answer in some cases and a more indepth diagnostic is needed
in some cases if you are under dealer warranty they may say there is nothing they can do because there is no "check engine light" but it doesn't take a brainiac to do some simple checking of what sensor is reading differently-versus-actual
this tells you/no, yes the thermostat is stuck open/closed, or no the temp sensor is giving a false reading, or no the ecm is not getting the correct reading (bad wiring), etc, etc
when it is intermittent that makes it even harder to troubleshoot (as usual)
doing the thermostat is easy and/or temp sensor and in most cases no further issue's happen, it's when you get a mixed bag and it keeps happening repeatedly that it becomes a headache, best thing to do in any case is use oem parts and there is a rash of bad ones out there regardless as noted by people having to replace them over and over and over sometimes.
funny thing is it started in 2014 with the change in engine design and vehicle software with the silverado's and in 2015 with the suv's, so system design has played a part.