Coolant temp gauge vs OBD2

Nascarnate326 · November 7, 2019

Driving my 2014 Silverado LTZ 5.3 I have noticed the coolant temp gauge shows much warmer temperatures than the OBD2 scan tool reports.

while the gauge shows between 160 and 210 my hand held scanner shows live data of 150 ish.

Do these trucks have two coolant temp sensors ? Where do your trucks run on the gauge ?

paumat · November 7, 2019

Dash temp gauge is likely not very accurate.

separately, have you owned the vehicle for all 172k miles? I have not seen one that high yet.

1SLOW1500 · November 7, 2019

150 is low doesn't sound right.

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gone_fishing · November 7, 2019

What you see is similar to what I have noticed when comparing the dash gauge to what my ScanGauge reads. I think the dash gauge is programmed to have the needle at the 12:00 position withing a certain temp range. Seems like once you hit 180ish the needle is at the 12:00 position. Basically anything between 180 and 210 the needle shows the same. I have noticed the voltage display is pretty accurate and matches the ScanGauge reading. Can't compare oil as I haven't been able to read that with my ScanGauge.

Side note: Over the last year or so I was noticing coolant was rarely getting above 185F on my ScanGauge. If I was towing in 5th gear then I would get up higher but regular cruising I was always a little lower. Decided to replace the thermostat and now I'm back up around 202-204.

1SLOW1500 · November 7, 2019

What you see is similar to what I have noticed when comparing the dash gauge to what my ScanGauge reads. I think the dash gauge is programmed to have the needle at the 12:00 position withing a certain temp range. Seems like once you hit 180ish the needle is at the 12:00 position. Basically anything between 180 and 210 the needle shows the same. I have noticed the voltage display is pretty accurate and matches the ScanGauge reading. Can't compare oil as I haven't been able to read that with my ScanGauge.

Side note: Over the last year or so I was noticing coolant was rarely getting above 185F on my ScanGauge. If I was towing in 5th gear then I would get up higher but regular cruising I was always a little lower. Decided to replace the thermostat and now I'm back up around 202-204.

Why to you want the high egt? 180 it about perfect. In fact may people with built or power mods go lower stat. There is no gain in higher temps. I watch mine and want 180ish asap as it effects tune. Then no more. I have lower stat. Supercharger guys have even lower stats to fight off high IAT and heat soak.

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gone_fishing · November 7, 2019

10 minutes ago, 1SLOW1500 said:

Why to you want the high egt? 180 it about perfect. In fact may people with built or power mods go lower stat. There is no gain in higher temps. I watch mine and want 180ish asap as it effects tune. Then no more. I have lower stat. Supercharger guys have even lower stats to fight off high IAT and heat soak.

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The lower coolant temps were fine during the summer but I had concerns about running that low during the winter. As it started to cool down this fall I was seeing 170ish temps when cruising. Wasn't sure how low it would go so I decided to replace the t-stat the same time I did a coolant drain.

CamGTP · November 7, 2019

If vehicles could run at 250 degrees, you can bet your ass that they would do it if they could. The hotter the engine the better the fuel economy would be but that just isn't going to be possible with the current style cooling systems and fuel we use.

There is no significant difference in performance from 180 degrees to 200 degrees. If you think that is a lie then maybe take a look at many of GM's performance cars that run stock 190-195 degree thermostat while also making 650hp straight off the showroom floor. It is not uncommon to see factory corvettes running 195-215 degrees while hooked up to a data logger.

If you've been around the GM V8 platform enough, mainly with being a technician or tuner. The gauge to OBD2 read out is always different by a little amount. Especially when cold, if you watch the gauge and as soon as it comes off the 160º mark the scan tool read out will still be around 130-145º almost always. Then as it reaches the 210º mark the temp is generally 10-15º cooler on avg. It's been like this on the P01/P59 and E67/E38/E92 controllers. The newest trucks seems to have gotten better from what I've seen.

Nascarnate326 · November 7, 2019

9 hours ago, paumat said:

Dash temp gauge is likely not very accurate.

separately, have you owned the vehicle for all 172k miles? I have not seen one that high yet.

I have no had it the whole time, I bought it used. I wanted the highest mileage LTZ I could find...let someone else take the depreciation.

Nascarnate326 · November 7, 2019

After watching a few videos I am thinking someone put a 160 degree T stat in previously. Since I live in Michigan and I dont know 100% of the trucks history I will have to throw in a new one and fresh dex cool.

Looks pretty simple, do you fill these newer trucks with the reservoir or the radiator first?