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Discussion Starter · #1 ·
I have an 07 Z06 that I got back in May of this year; it had just under 39k miles on it when I purchased it and right now it's somewhere close to 45k.
In the last month or so I've noticed that when I'm cruising the coolant temp stays between 217 and 223 depending on the speed I'm running but coming to a stop it shoots up almost instantaneously to just under 230, between 225 and 230 most of the time. I really don't recall it ever having this much fluctuation... I've always kept a pretty close eye on it and I don't recall it ever getting much over 220 or 221 up until recently.

I've checked for airflow obstructions and I've watched the thermostat cycle using a IR thermometer.
The fan comes on somewhere around 225 but it seems like it always stays on high (as I understand it these fans have an auto speed adjust).
I've seen in other forums where the temp should not exceed 220, and is usually somewhere between 212 and 217, is that under load or is that idling?
What is the standard idling temp for these things after it's warmed up? What is the standard temp with this car under load, after warm up?

Since the car is getting close to 50k, should I go ahead and get a coolant service done?
Lastly, does anyone know any good Vette mechanics in the Nashville, TN area?

I'm probably just being overprotective getting myself worked up for nothing.
Any feedback or input would be greatly appreciated.

Chuck
 

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Z06 Tech Advisor
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You need to understand how GM commands the coolant fans, which is within the PM calibration
PCM commands what the percentage of the fan's rotation is
Looking within your Z06, the fans are only commanded to rotate 14.9% and that does not begin until 219 F deg
And does not go even then 89.9% speed of rotation until 233 Deg

PCM will also command the fans higher rotation when the A/C is on, so you may see cooler temps then and now with it off the temps can be higher

If wanting the temps to be lower than have someone tune the PCM calibration and change the values shown below
Stock Tstat is like 192 deg so as you see the coolest temp PCM can command is 89 C so with tune start commands fans on then and up the rotation throughout this table

Also swap Tstat with like a 175 % and with setting higher fans rotation will help bring down the engine bay temps
which also means the air in intake and gas in fuel rails be cooler and better charge to the cylinders

Only reason GM forces the higher temps is for smog reason but learned their lessons as look at the design of C8 which has more and larger coolers and engine temps run cooler

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For one thing your car is going on 16 years !! You should have changed your coolant 3X's already to this point and is due now also. I would also put in a new tstat,but NOT a 175. You will eventually have issues. GM engineered motor to run optimum in the 195-210 range.
 

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GM does NOT optimize the calibrations, they can care less about performance
Their calibrations are about meeting SMOG and to limit GM new warranty claims

Any GM vehicle will gain on average 30 HP gains for an all stock engine with a PCM tune.
C8s coolant now run cooler than past Corvette gens so the run hot cyberspace theory is not valid
Engine makes more power with colder air/fuel charges to cylinder, not hotter and by running cooler
reduces lean AFRs which then take some load off the fuel injectors that are a bit too small to handle long
term high RPM/loads, such as in racing.

Lastly, GM learned the hard way with the lost class action lawsuits of Z06 owners who when racing due
to hot coolants caused PCM to go into limp mode and reason C8 is designed to run much cooler and a Tstat of 175 Deg is not going to prevent the fans control by PCM to run less than 89 C if PCM is tuned
 

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Discussion Starter · #5 ·
For one thing your car is going on 16 years !! You should have changed your coolant 3X's already to this point and is due now also. I would also put in a new tstat,but NOT a 175. You will eventually have issues. GM engineered motor to run optimum in the 195-210 range.
Thanks for the info! I bought the car in May and I have a folder with all the service records; it has been serviced a couple times between being sold new and now.
You think that the age is a factor on why it's running hotter that what I think it should? To my knowledge, since I purchased the car, I've never seen it anywhere near 195-210 once it's warmed up.
I planned on getting it serviced once it hits 50k miles but I'm certainly fine with doing it sooner if you think it will help the current issue.
 

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Discussion Starter · #6 ·
GM does NOT optimize the calibrations, they can care less about performance
Their calibrations are about meeting SMOG and to limit GM new warranty claims

Any GM vehicle will gain on average 30 HP gains for an all stock engine with a PCM tune.
C8s coolant now run cooler than past Corvette gens so the run hot cyberspace theory is not valid
Engine makes more power with colder air/fuel charges to cylinder, not hotter and by running cooler
reduces lean AFRs which then take some load off the fuel injectors that are a bit too small to handle long
term high RPM/loads, such as in racing.

Lastly, GM learned the hard way with the lost class action lawsuits of Z06 owners who when racing due
to hot coolants caused PCM to go into limp mode and reason C8 is designed to run much cooler and a Tstat of 175 Deg is not going to prevent the fans control by PCM to run less than 89 C if PCM is tuned
I'm open to any and all suggestions, just don't want to screw the car up.
This is the first one I've owned and I looked for a really long time to find it.
Thanks very much for the input.
 

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  • Specially formulated optimum service intervals, the coolant can last up to 5 years or 150,000 miles. (Maintenance needs vary with different uses and driving conditions. See your Owner's Manual for more information)
  • Helps provide resistance to corrosion by protecting brass, cast iron, steel, solder, and copper components. Also provides superior high-temperature protection for aluminum components
  • Non-silicate formula retains excellent heat transfer characteristics for optimum water pump life
  • Long shelf life: storage-stable for 8 years
If past owner did proper maintenance and kept records, see when they last changed the Dex-Cool
Being a simple job you could just change it and go from there but of course is weather cooling down
you might not see higher temps till next summer

But the 427 CI LS7s always run hotter coolant temps and if not getting warning on DIC then you're seeing close to normal readings
 

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I have an 07 Z06 that I got back in May of this year; it had just under 39k miles on it when I purchased it and right now it's somewhere close to 45k.
In the last month or so I've noticed that when I'm cruising the coolant temp stays between 217 and 223 depending on the speed I'm running but coming to a stop it shoots up almost instantaneously to just under 230, between 225 and 230 most of the time. I really don't recall it ever having this much fluctuation... I've always kept a pretty close eye on it and I don't recall it ever getting much over 220 or 221 up until recently.

I've checked for airflow obstructions and I've watched the thermostat cycle using a IR thermometer.
The fan comes on somewhere around 225 but it seems like it always stays on high (as I understand it these fans have an auto speed adjust).
I've seen in other forums where the temp should not exceed 220, and is usually somewhere between 212 and 217, is that under load or is that idling?
What is the standard idling temp for these things after it's warmed up? What is the standard temp with this car under load, after warm up?

Since the car is getting close to 50k, should I go ahead and get a coolant service done?
Lastly, does anyone know any good Vette mechanics in the Nashville, TN area?

I'm probably just being overprotective getting myself worked up for nothing.
Any feedback or input would be greatly appreciated.

Chuck
Hello, Jonathan here, (Victory Red, 09 ZO6)
Car Wheel Vehicle Land vehicle Automotive parking light

Wheel Tire Vehicle Car Automotive parking light

I have an 07 Z06 that I got back in May of this year; it had just under 39k miles on it when I purchased it and right now it's somewhere close to 45k.
In the last month or so I've noticed that when I'm cruising the coolant temp stays between 217 and 223 depending on the speed I'm running but coming to a stop it shoots up almost instantaneously to just under 230, between 225 and 230 most of the time. I really don't recall it ever having this much fluctuation... I've always kept a pretty close eye on it and I don't recall it ever getting much over 220 or 221 up until recently.

I've checked for airflow obstructions and I've watched the thermostat cycle using a IR thermometer.
The fan comes on somewhere around 225 but it seems like it always stays on high (as I understand it these fans have an auto speed adjust).
I've seen in other forums where the temp should not exceed 220, and is usually somewhere between 212 and 217, is that under load or is that idling?
What is the standard idling temp for these things after it's warmed up? What is the standard temp with this car under load, after warm up?

Since the car is getting close to 50k, should I go ahead and get a coolant service done?
Lastly, does anyone know any good Vette mechanics in the Nashville, TN area?

I'm probably just being overprotective getting myself worked up for nothing.
Any feedback or input would be greatly appreciated.

Chuck
Good morning! Jonathan here,(615.587.0943) from Hendersonville TN.

I don't check the Forum every day, best to call or text, if you'd like to talk.

I've had some "issues" with my 09 ZO6 cooling.

I'd rather talk on phone than fill in all the information, here...



Currently have 2 Vettes with 427s, an 05 with a fairly modified 08, 6.2 with LS7 ported heads, and accompanying upgrades, cam,etc., .

An 09 Z06, with American Heritage Racing heads, Billy Boat mufflers, otherwise stick drivetrain.

That said, I have 2 area Mechanics that I use.

#1 , Wesley Hendley 615-587-1746, Goodlettsville TN, formerly worked for KMF Racing Engines of Dickson TN.

He now Owns the Business.

He built the 08, 6.2/7.0 heads , 521 rwhp engine and installed it and the accompanying drivetrain upgrades. All NA.

It's a screamer!

#2 is Erin Carpenter, of CARMA PERFORMANCE, 1035 3rd Avenue S. Nashville Tennessee 37210
615-730-8654, he tuned the 6.2/7.0 and adjusted drive-ability issues.

He really stands behind his work!

Tell him Wesley and Jonathan Hendley, blue 05 w that 6.2/7.0 heads engine, sent you.

He and his Shop do all kinds of performance upgrades and tuning, with lots of C5/C6,C7 experience.

#3 is Not local, but he is a Expert imhop on C6s and Z06 s.

Stephen Gilbert, of Southhaven Mississippi, rt by Memphis. I'd need to give him a heads-up if you want to talk to him, as he doesn't answer calls from unknown #s.

Best to you, glad to help a Brother in Vettes if I can,

Jonathan
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Just to give you a reference, I took my car out this past Monday our temps were around the upper 40's low 50's. I was on the highway running 75 ish and watched my coolant temp climb to 198*. Shortly after that the fans must have kicked on and the temp dropped quickly to 192*-194* and stayed there. My car been tuned and my fans come on earlier and run faster the the stock program.
I change my coolant and brake fluid every 3 years now. If you ever see what expired coolant or contaminated brake fluid do to your car, you will find that changing them early and on a regular basis will save you a lot of headaches.
My car is a '13 with 15,500 miles on the odometer, it will sit from mid December until usually mid March. Lots of idle time for things to go wrong.
 
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