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Just got my new (to me) 98.5 on the road. The coolant temp is maxing out at 165 no matter what type of driving that I am doing. Is the truck running a bit cool?
 

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These thing do run cool, but that is kind of low, I wonder if the PO put in a 160 T-stat. Mine normally runs 195 but will drop to 185 if I sit at a long traffic light.
 

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Thanks Syco. I pulled the thermostat and it had a 180 in it.I put a 190 thermostat in....I'll see how that does. Maybe temp gauge isnt reading right because it def didn't get to 180 at all.
 

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It takes a good half an hour of driving to get up to temp, won't do it at idle. It should hold 190-95 when driving normal. idling or down hill it will drop a bit sometimes(only 5-10 deg.). In winter, just idling the heater core will cool below normal if heater fan is running. You definitely need 190-95 stat.
 

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Thanks Bigfish that is exactly what I am seeing now. I am used to my temp gauge staying at a certain temp but it seems to bounce around between 180 and 205 now with the 190 thermostat. Thanks for the responses.
 

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You will probably see a 2 mpg increase with a 190 now.
 

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Also, the temp swings on the gauge are normal.
 

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Another thought if there is any air in it at all it can throw off the sensor reading because it is at the high point and without water contact it will show low. So warm it up with the cap loose and make sure it is fully full and close it and make surer the over flow tank is proper level.
 

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The air will flow right out as thermostat opens and if done with cap loose you can fill it right then until airless and full. Otherwise it it takes 2-4 heat cycles to expel air through overflow and suck coolant back in. Air does not hold in the system once circulation is achieved. The cap neck is the highest spot and it will push out there with each heat expansion.
The exception is if there is a leak in the water pump, radiator or elsewhere that air can suck back in easier than the coolant from the overflow tank(or it is empty).
 
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