1990 5.7. When I put my temperature gun to the sensor or the t-stat housing it reads 160-170 give or take. When I check the other sensor near exhaust it reads any where from 220- 260. What should this sensors temp be reading? 210? My engine running hot?
Coolant temps
- Thread starter Munch
- Start date
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Well, of course none of these sensors are calibrated so, you just have to go with your best guess. I know my digital dash gauge will show 210 when the sensor next to the T-stat going to the ECM reads 194 (the same as the temp my T-stat is supposed to be). When sitting at idle with the A/C on in 105 ambient, the one in the head starts to rise up to 220 while the ECM reads 198. This is with a high flow water pump, T-stat, and 3-row aluminum radiator. As soon as I rev it up to 1800RPM it cools back down to 210 on the gauge. IMO there's not as much flow or coolant in the head (or it's generating more heat) as in the water jacket. GM says it's overheating when it goes over 230, IIRC.
Also be cautious about using IR temp gun as they are also influenced by the emissivity of whatever they’re pointing at. They also take their measurement from a much wider area than the little laser dot would lead you to believe. Consider panting the two sensors in flat black paint, or better yet try a contact thermocouple. I suspect the measurement by the exhaust manifold is getting influenced by the exhaust heat. Another idea, you could take the sensors out of the engine and “calibrate” them by sticking them in ice water and boiling water while measuring their resistance. If their resistance measures the same I would expect them to report very similar temperatures.
Trigger_guard
I'm Awesome
Yeah,. The temperature gauge gives a rough average. (Like the fuel gauge). Otherwise it would move Everytime you put ur foot down.
The gauge will read sightly higher than the ecm. As the coolant is hottest in the head.
Reading the outside of the sensor with a heat gun will never give u an accurate reading.
As with most factory gauges take with a grain of salt. Worry about changes more than the numbers. I.e. if it always ran at 205ish. And now it's running at 215ish. I may not be overheating technically,. But something has changed. And needs looked into
Oh. And when in doubt. You can always stick a mechanical gauge in passenger side head as a reference
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The gauge will read sightly higher than the ecm. As the coolant is hottest in the head.
Reading the outside of the sensor with a heat gun will never give u an accurate reading.
As with most factory gauges take with a grain of salt. Worry about changes more than the numbers. I.e. if it always ran at 205ish. And now it's running at 215ish. I may not be overheating technically,. But something has changed. And needs looked into
Oh. And when in doubt. You can always stick a mechanical gauge in passenger side head as a reference
Sent from my SM-N960U using Tapatalk
Last edited:
Ken K
I'm Awesome
The further back you are, the less accurate your "IR" gun will be as they have a Focus Point". Also, you are reading the outside of metal, not the coolant inside and on top of a thermostat, this would be the colder side, unit the "T-Stat" opens.
I guess my question is, what is the reason you are checking the engine coolant temperature for? Is it for gauge accuracy, new digital cluster, electric fan controller?
As stated, I would use a scan tool to check actual coolant temp reading. Just keep in mind, the parts stores use different tools to "Read Codes" but most likely do not have coolant temp access.
Just curious as some post do not have enough info to know where to go to provide an answer for your exact concern.
I'm looking into this 1 because I have no running history with this truck. Bought it a few years ago. Only drove it once from few houses away and tore it apart. Finally got it back together with new engine, paint, interior. 2 the gauge in the truck is reading 240. So that has me concerned. The sensor near the exhaust is brand new and I noticed when I unplugged it the gauge goes to zero. So I assume this sensor is for the gauge and the other sensor next to the t-stat is for the computer.
Mechanical autometer gauge is my next step I think.
