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Discussion Starter · #1 ·
Hi guys, I need help. I’m working on my late husbands truck and I’m having an issue with the gauge, or the coolant temp. It’s a 97 Silverado k1500 5.7 Vortec, engine powered fan. I replaced the temp sensor on the drivers side block Becuz the dash gauge didn’t work, I replaced the thermostat with a 195, the temp sensor by the thermostat housing as well. I also had to put in a new heater core Becuz it hasnt worked in yrs. I also flushed the coolant. I wasn’t able to find the drains for the block though. I did run water through the radiator and heater core hoses till it ran clear though. In and out of both heater core hoses. Burped everything. Gauge now works but goes 3/4 hot. I used laser to shoot on the engine and radiator and got number all over. Radiator was 80’s. Thermostat housing was 170 ish, directly on the temp sensor on the drivers side was 245. Right next to that was 260 and exhaust head was 350’s. I can’t for the life of me figure out if my engine is ok and the gauge is bad or if the engine is running that hot. Please help me.
 

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you might just need to be patient as computer is relearning new temp gauge sensor , i recently changed out oil pressure sensor , and the gauge was doing same for about a day , then started working correctly.

i think you engine temp is fine , drive it for a day , use lazer and check often , see if it settles down

you said you burped the system , make sure your over flow bottle is at correct level , it also may be just more air in the system, warm it up to running temp , let the thermostat open, and turn temp gauge to heat , let the full cooling system circulate
 

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I'm with Brian, I think you might have more air in the system.
Try parking with the nose higher than the rear and let it idle for awhile.
 

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Discussion Starter · #4 ·
Hey thanks so much for replying back. I did try parking it nose up to get the rest of the air out, ran it with the heater going. I’ve been keeping an eye on the coolant level for a few days but my gauge just keeps saying the high temps. Did I test the temps in the right places to get accurate engine temps? I’m worried I may have a small leak somewhere. Would that cause the gauge to read like that?
 

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I suspect you don't know how the gauge read before you started, you could have a bad gauge

By the way, check the temp range on your laser gun, my gun was reading all over the place as well when I used on the engine, then I discovered it had an upper range that was lower than the normal engine temps.
 

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Sorry Heather, I read that part and then forgot, guess I assumed where it was your husband's truck he drove it and you didn't.

Do you have access to a multimeter to read resistance, we could test the sensor?
 

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Discussion Starter · #8 ·
Weird, I posted a reply but now it’s not showing. Anyway, I do have a multimeter. I’m not good at using it at all Ray 🤪 I can use it if you tell me specifically what I need to have it on and what to do.
Your right on the whole me not driving it thing. I rarely drove it when he was alive. I do know that it didnt work then and neither did the heater.
 

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It's easy to use, we can walk you through it.

The temp sensor changes resistance as the liquid changes temperature. A resistance reading is all the computer uses to monitor the temperature.
The computer is also connected to the gauge in the dash and as the sensor changes resistance the computer changes the voltage to the gauge.
I'll find some charts that will let us know what resistance we should see.

Heather, a quick question, when you changed the temp sensor did you us any sealant on the threads?

And, how is the heater working now?
 

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Discussion Starter · #10 ·
I didn’t put anything on the threads. It has its own stuff so I just installed it as is. Looks like this one in the picture basically. The heater is HOT now. I think it has some issues with the actuators or blend door Becuz I can feel the heat even when the blowers off. It’s like it doesn’t seal off. But other than that the actual heat itself is great.
169649
 

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Ok perfect, that's the right way to install it.

I've been busy all day, let me see if I can find the resistance chart
 

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Ok Heather, here is a chart of the resistance at different temperatures.

Just select the Ohm scale on the meter, touch the 2 leads together to be sure the meter reads 0.
Then you need to disconnect the temp sensor.
Then read the resistance of the temp sensor while the engine is cold, jot it down and the air temp.
Then run the engine until it is hot and read the resistance again, and jot it down.
Compare both reading to the chart below.
Let us know the results.

169654
 

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^^^X2. You can also pull the sensor and read the resistance in room temperature. Then dip it in boiling water, it should read 177 Ohms (100*C or 212*F) as per Ray's chart.
 
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