temperature gauge fluctuates? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

85sierraclassic · 10-03-2011, 10:39 PM

hey all,
so today i finally decided to replace my heater core and put a thermostat back in. i got everything done and filled it all back up with a 50/50 mix and let it run till the thermostat opened and added coolent as needed and what not. the temperature seemed right, bout 195 or so it opened and dropped back down to 160 or so then came up some and leveled out bout 180 or so but after driving a little it seems like it comes up to about 190/195 then drops to about 160/165 and just kinda every 20/30 seconds it goes back and forth. i had the heater on high the whole time threw out all of this but dont see why its flucuates so much?

10-03-2011, 10:39 PM	#1
85sierraclassic Registered User Join Date: Dec 2010 Location: auburn ne Posts: 230	temperature gauge fluctuates? hey all, so today i finally decided to replace my heater core and put a thermostat back in. i got everything done and filled it all back up with a 50/50 mix and let it run till the thermostat opened and added coolent as needed and what not. the temperature seemed right, bout 195 or so it opened and dropped back down to 160 or so then came up some and leveled out bout 180 or so but after driving a little it seems like it comes up to about 190/195 then drops to about 160/165 and just kinda every 20/30 seconds it goes back and forth. i had the heater on high the whole time threw out all of this but dont see why its flucuates so much? __________________ 85 GMC sierra classic : 350, 4spd, 205, 3.42s, 35s



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