Fan running at shutoff suddenly
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Joined: Feb 2023
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Fan running at shutoff suddenly
Hello, I’ve had my ‘16 Z51 for a year now and suddenly (within the last week) the fan is running after shutting down from anything over a 5 minute drive. The temps are running in the 220-235 range which I’ve read is normal, but it hasn’t done that until now. And that’s including a Phoenix summer last year. It’s starting to get hot here, but barely cracking 100°. The thermostat went out last year and I replaced it in November. I forgot to check my coolant levels after refilling at the time. Checked on Friday and the reservoir was nearly empty. Topped it off but still having the high temps. Watching the gauge, it’ll steadily climb to 190, then pretty quickly hit 200 and 220. Hovers around there but will go to 235 briefly. During normal driving. A/c on or off. Coasting (M7) doesn’t help it cool down. Wondering if the coolant temperature sensor could be going wonky, or if the Napa thermostat I used is already a problem. Thoughts?
Melting Slicks
Joined: Feb 2018
Posts: 2,198
Likes: 1,057
From: North Texas
Is the engine really that hot?
Take a IR temp gun and read some temps around the engine, hoses, radiator.
If hot:
You might have air in the system, you could try to run a vacuum device to try and help remove any air that is trapped.
Bad thermostat.
Bad temp sender.
Take a IR temp gun and read some temps around the engine, hoses, radiator.
If hot:
You might have air in the system, you could try to run a vacuum device to try and help remove any air that is trapped.
Bad thermostat.
Bad temp sender.
Safety Car
Joined: Dec 2012
Posts: 3,875
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From: St. Louis Metro East IL
With a good OEM thermostat the temp should ramp up to around 190 - 195 F and then stay there while driving. In very hot weather or slow traffic the temp may go up to 220 or so until you start moving again and get the rpms up a bit.
The fan should run a bit if the temps are as high as you noted.
OEM thermostat: GM# 12674634 / AC Delco 15-11113
Ron
The fan should run a bit if the temps are as high as you noted.
OEM thermostat: GM# 12674634 / AC Delco 15-11113
Ron
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Today I bought a new AC Delco Coolant Temp Sensor, replaced it, reset the system, and took it for a drive. In about 6 miles of street driving (at night, so no real traffic), it hit 240. Essentially no change. Also today, it was hitting 250 and once hit 260 before falling back to 240. The erratic behavior of the temps made me think it was the sensor, but now that it's been replaced, I'm wondering if it's the thermostat. The thing that's throwing me off is the oil temp is sitting right around 240. I'd expect oil to be hotter than the coolant at any given temp.
Safety Car
Joined: Dec 2012
Posts: 3,875
Likes: 1,874
From: St. Louis Metro East IL
Sounds like a sticking / stuck thermostat. Replace it.
Since your oil temp tracks coolant temp the oil and coolant temp sensors are working.
My oil temp tracks coolant temp, but is usually lower by a few degrees. Oil temp might get above coolant temp in stop and go traffic.
Ron
Since your oil temp tracks coolant temp the oil and coolant temp sensors are working.
My oil temp tracks coolant temp, but is usually lower by a few degrees. Oil temp might get above coolant temp in stop and go traffic.
Ron
Tech Contributor
Joined: Oct 1999
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From: Charlotte, NC (formerly Endicott, NY)
However, the OP does need to make sure the coolant-to-water ratio is 40/60 as that is what the C7 engines require. 50/50 mix will cause the engine to run hotter since coolant doesn't transfer heat as well as water does.
Bill
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Well, I checked the dispstick. Fortunately (or unfortunately) I just did an oil change about 2 weeks ago. No sign of the oil scorching. I used the typical Mobil 1 5w-30. It was still a new amber color and smelled normal. Also don’t see any signs of coolant leaks exterior. Of course, it’s possible that the head gaskets could leak internally.
Temps have been fine for the past week with the new thermostat. The 260° it hit for a few seconds, like 3 or 4. Oil temps though were in the 245-250 range for an extended period.
From what I can tell, it’s mixed whether the oil should be changed or not. Mobil 1 burns off at 500° from their info. And aside from the few seconds at 260°, it was never in the red on the gauge.
Temps have been fine for the past week with the new thermostat. The 260° it hit for a few seconds, like 3 or 4. Oil temps though were in the 245-250 range for an extended period.
From what I can tell, it’s mixed whether the oil should be changed or not. Mobil 1 burns off at 500° from their info. And aside from the few seconds at 260°, it was never in the red on the gauge.
Melting Slicks
Joined: Feb 2018
Posts: 2,198
Likes: 1,057
From: North Texas
FYI: always check a new thermostat.
Stove, pan of water, thermometer, vary temp up and down and watch the opening and closing of the thermostat a few cycles. And always check for binding by hand, make sure it closes completely, check with light source. If all checks out, install. Vacuum system, add coolant. Good to go.
Stove, pan of water, thermometer, vary temp up and down and watch the opening and closing of the thermostat a few cycles. And always check for binding by hand, make sure it closes completely, check with light source. If all checks out, install. Vacuum system, add coolant. Good to go.