Jaykoh-Z51

2015 Z51 M7. 27,000 miles


Sunny day. Mid 70s. I wasn't driving hard. I was on a phone call and needed to pull over and stop to write some info down. Sat in a shaded area for maybe 5 minutes at idle. Noticed the AC stopped blowing cold air. Then I noticed the engine temp (permanent needle gauge) was at 260. My car NEVER runs hot. Usually steady at 200. Maybe 210 while in stop n go in mid summer in epic traffic in Atlanta.

When I started driving again, engine temp creeped back down and the AC resumed normal operation.

So, last two days I've been watching the engine temp. Now it's been hovering at 205-210. I always watched it before and I KNOW it's always been steady at 200 prior to the temp spike.

Any ideas?

I'll probably take it by Chevy soon when I can find time.

C82LT

Thermostat needs to be replaced.

genesis_1086

My previously owned 15 Z51 had a similar issue. Apparently, my radiator cap wasn't fully tightened and half a gallon of coolant had escaped according to the dealership.

HAD2HAV2

I'll be interested in what the dealer finds as my 2015 has done the tried to overheat also. Wasn't the stat or the cap. No reason was found.

Jaykoh-Z51

Update:

just had had her at the dealer. Could not duplicate.

Of course

I explained to a couple techs that this car, since I've owned it, has had a rock steady engine temp of 200. Maybe 205-210 after a hard acceleration tops. But lately the temp range has been "sloppy".

Sooooo, this other tech would like to have it for longer when it's convenient for me. The next few weeks suck for timing plus I have a road trip from Atlanta to Daytona in 4 weeks.

2K14C7

Possibly a computer glitch not turning on the fan?

Jaykoh-Z51

Perhaps. But seems like the temperature hasn't been as dialed in as before.

Avanti

I had what sounds like an identical issue once and only once with my '01 C5... though, I never monitored the temps that closely, before or after. So, I cannot speak to that aspect.

However, after I thought about the issue at the time, I was not sure that the fans had turned on when it overheated. As I say, this has never happened again in the intervening 7 or 8 years. I still have and drive the car semi-regularly without further incident.

HAD2HAV2

Please us informed when you take your car back to the dealer.

Jaykoh-Z51

Driving home tonight. 75 degrees. She went to just a needle width below 255.

Sigh

next drive it was normal.

i don't think the fan was running

NSC5

Were you in stop and go traffic when it approached overheating tonight? It shouldn't be dependent upon the fan for cooling once you are cruising at 30MPH or greater but it does need to be functional for stop and go type driving.

When the temperature goes that high the fan should be screaming at near maximum speed and easily audible with the car at idle.

Jaykoh-Z51

I was on the interstate for a little...20 minutes. Temp rose quick from engine start to getting on the interstate to about 215. Quicker than I recall on previous normal days.

While at speed, temp was 215ish.

Then after I exited the freeway I was in some minor stop and go. Nothing crazy. Thats when it began to creep up eventually hitting 255. Cant say for sure if the fan was on then. The A/C was on and actually NEVER kicked off while the temp hovered in the 250s.

Next drive (about an hour later), I definitely heard the fan and the temp stayed around 215.

Dealer visit tomorrow.

MrVetteAddiction

Had the same thing with my 2015. I could tell the fan was not turning on. Would do it every now and then in traffic and dealer always responded cannot duplicate. (Funny thing is I turned on the PDR and they never drove it in traffic so of course it was not going to duplicate). Finally had my wife record it when it happened to give them proof. Still gave me the cannot duplicate. I told GM customer service I was not accepting the vehicle back until they started replacing parts since it was the 3rd time. They replaced the fan relay/switch after talking with the Corvette engineers and seemed to cure the problem. I will end this with the worst part of Corvette ownership is Service which just sucks.

Jaykoh-Z51

I took a bunch of pics. They'll see it tomorrow when I show them.

Jaykoh-Z51

i know all of you are the edge of your seats about this. LOL

They're hooking up a bunch of sensors to her then going for a drive. Possibly a rogue indication. No codes came up from interrogation.

Who knows...

NSC5

If it is just a rogue indication (engine coolant) then the oil temperature won't go up above its typical temperature but I expect it will rise above its typical reading also indicating a real issue and not just a faulty coolant temperature sensor. With the oil to coolant heat exchanger the two temperature changes will tend to track together over the medium to long-run in the C7.

With the driving you were doing coupled with ambient temperature this time of year you were probably just on the cusp of a "limp" overheat and continued low speed driving and extensive idling would have caused the overheat condition. The sensors are more reliable than relays, fan motors, thermostats, etc. so generally an overheat indication really is an overheat condition.

snomuncher

Ask the dealer to check the A/C pressures with their scan tool and compare them to expected values. A/C pressures are one of the triggers that starts the fan. If your A/C was not blowing cold when the overheat happened, it might be related to the A/C system.

kenownr

OP: I hope they find it for you. I used to live in ATL, nothing worse than over-heat in ATL traffic on I-75 or I-285 in the middle of 6 lane traffic, no place to go, and for sure nobody will let you over!!
I kind of agree with several posts above, it sounds like your fan is not coming on and it's intermittent.
Best of luck and I hope they find it.

Nexxussian

As I am still studying these (as opposed to having one) I'm curious to know if it's possible on the initial overheat (260° ) some coolant escaped.

I ask as it makes me suspect there could be a small amount of "air" in the system.

I've never had an air lock in a cooling system of any GM product I've used, ever, but is that a possibility?

I know an indication problem is far more likely, but, if it turns out to be not an indication problem, could they try pulling a vacuum on the cooling system and see what the coolant level does when it is released?

For clarity, I do mean a hard vacuum like I could do with a Mity-Vac, I'm sure they have something fancier.

CP

Is this to determine how hot your wife is? What about the car?