Temperature gauge fluctuating

White96k2500 said:

okay so my temperature gauge problems started last year, when i would get in my truck to go to school when i get about 10-15 minutes from the house and I’m driving it would get to normal operating temp (around 195) it would automatically rise up to right at 280 and drop right back down to 195 then right back to 280 and drop down again then after that it will be fine the rest of the ride and i put a new thermostat in it last year and it was good until now and is doing the same thing again so from what I understand from what I’ve been readingeither the thermostat is bad again or thecoolant temperature sensor is bad any helpwill be greatly appreciated, truck is a 96k2500 with the 5.7 vortec

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Rick Gill said:

This may seem crazy, but it is somethng I did on my truck! I put the thermostat in backwards! When you do that, the temps fluctuate wildly! Just check to make sure you've got the sensor side pointing into the block.

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scottydl said:

I've had all sorts of inaccurate temp sensor issues on my Suburban. It's got the 7.4L so not the same engine as yours, but most of the stuff everyone already suggested are the same things I checked & replaced on mine. Originally I thought the gauge was reading too low, but it turned out it was fairly accurate and a radiator flush (got all sorts of brown gunk out) had actually helped the engine run cooler. One way to check engine temperature is with a laser infrared thermometer (I bought this one from Amazon) and point it at the thermostat housing when the engine is hot and running. See if that matches the dash gauge.

Are you losing any coolant, even small amounts that you can smell when the engine is hot or right after you shut it off? Recently my gauge was all over the place like you described, I could smell coolant, and it turned out that the water pump was bad & leaking. The loss of pressure in the cooling system was keeping the coolant from circulating and making the gauge go all wacky. So check that out too.

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White96k2500 said:

i have noticed that when i shut the truck off and get out and walk past i can smell some coolant put I haven’t seen or noticed any leaking

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Oldblue98 said:

Are you having to add coolant ?

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White96k2500 said:

I was having to but haven’t in a while but the main thing i don’t understand is my temp gauge only acts up in the winter

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Oldblue98 said:

Yes I understood the main question, but mainly I was referring to the smell of coolant and no visible leak. Mine was intake gaskets. But also when I had gauge issues, I replaced my air core motors in the gauges and solved my problem of gauge swing and flicker.

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White96k2500 said:

Well Old blue i believe i do have a bad intake gasket this picture is back behind the water pump

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