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Fluctuating Coolant Temp

M

Mekaiyo

New member
I just now noticed in the winter, my car coolant temp sensor has been different. My car is not overheating but when I drive, the need fluctuates between 160-190. 2 lines above 160 and 2 lines below 190, it would move up and down. When idling, gauge goes to 190ish and stays there, any advice?
 


It's cold. When you drive your car, it will sit at a lower temp because air is constantly flowing over the engine cooling it. When at idle, no air is passing over it, so it slowly heats up. Not a big deal. These cars want to be operating at like 200* so you have nothing to worry about.
 
I have two 99s, a GT and a GTP. The S/C one seems to have more stable temps which makes sense. The N/A one moves around more and is generally a little cooler at least in cold weather. The thermostat on a GT is probably busier in winter because it can fade the engine heat more readily.
 
your Thermostat is cycling too much, ive seen it more with cheapo T stats.

its one reason modern cooling systems are "mixing" systems with the T stat affecting the cold water inlet to the block to keep the temps more stable. yours opens, lets the hot water into the radiator, cold water rushes in, t stat slams shut, tem rises, t stat pops, cycle repeats.
 
So if this is normal and I did not see this during spring and the summer, I don't have to worry about replacing the thermostat? During previous months, it would either be constant at 190F. Ever since winter hit, it fluctuates all the time now from 170-190
 


it is possible that the wax pellet inside your thermostat is dying. so yeah you could still need a thermostat but the problem would probably go away if you could block at least one third of the air flow through the radiator so that the coolant can not cool off as much. but that sort of a redneck remedy...
 
im thinking bout replacing my thermostat, so my temp sensor is fine?
Turbocharged400sbc said:
your Thermostat is cycling too much, ive seen it more with cheapo T stats.

its one reason modern cooling systems are "mixing" systems with the T stat affecting the cold water inlet to the block to keep the temps more stable. yours opens, lets the hot water into the radiator, cold water rushes in, t stat slams shut, tem rises, t stat pops, cycle repeats.
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I have also noticed especially on highway my temp gage flexuates about 1/4" with my 180 thermostat. Maybe I should replace mine too?
 
Mine goes to 1/4 now and stays there but fluctuates 1-2 lines below it, so it seems pretty normal now and not as bad before. I pleased my thermostat early in the morning
pshojo said:
I have also noticed especially on highway my temp gage flexuates about 1/4" with my 180 thermostat. Maybe I should replace mine too?
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You guys also should check through the obd2 for the actual coolant temp. My gauge will read 210, but obd2 says 230.
 
thekidinbuff said:
I do, it runs at 180. How is your car running so hot?
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My L67 likes to run at about 180 as well. I am thinking about switching the T stat. If I sit for a while it will get to about 185, then drop back down to 170, and then slowly start to get back to 180. I have also check it on my OBDII reader, and it really does read about 180 while cruising at 55mph on the back roads.
 
Nates94 said:
My L67 likes to run at about 180 as well. I am thinking about switching the T stat. If I sit for a while it will get to about 185, then drop back down to 170, and then slowly start to get back to 180. I have also check it on my OBDII reader, and it really does read about 180 while cruising at 55mph on the back roads.
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Let us know what you do and how it turns out. Its too cold here, im waiting for the weather to break.
 
Good to know this is normal. I am driving my Wifes 08 more and this has been driving me nuts. Even changed out the thermostat thinking it could be the issue. My Subaru just always stays at the middle mark once warm even in winter. Thought this was a issue with the car.
 


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