90VetteZR-1

Okay, so I had to go to drill today, only about 65 miles away, but I had to drive my Z. While I don't mind driving in the snow/ice in any car, (I'm confident in my driving ability) I didn't like the idea of potentially wrecking my Z, but it was the only option. At any rate, before I even got a half mile from my house, I noticed the temp gauge hovering a bit above the hashed area of the 260 degree mark for coolant temp. It scared me so I turned off the car, then turned it back on, and the temp gauge went back to around 200-ish degrees, somewhere near half, so I figured it was because I had the car idling to melt the ice and on the windows and the fans just hadn't turned off. It never touched the hash, so I figured everything was ok. Anyway, I continued driving, glancing at the temp every now and then, but the temp always stayed normal, but about 45-50 miles into the trip, the temp started climbing again, so I turned the car off again, let it coast for a bit, turned the car back on, and the temp slowly went back down to normal. So I continued to keep any eye on it, and had to turn it off two or three more times to keep the temp from getting into the hash area, however, I missed it once, and the temp got into the hash, and I think it was actually one the 260 degree line, but I immediately turned it off, let it coast, and the needle was immediately above the hash. This was about 10 miles or so from my destination, so I continued to keep a (closer) eye on the temp, but it never got close to the hash after that.

Now, my concern is that it got, I think, to the 260 degree line. The hash scares me enough. So, When I got to my destination, I popped the hood, laid my hand on the block, and it didn't feel any hotter than normal, no smoke from tailpipe, no busted hoses, no excess heat, nothing at of the ordinary. When I started researching why it could do that, I found several articles talking about how snow could block the radiator fans from getting air to the radiator, causing overheat issues. I'm not around my car to confirm this was the case, but considering this is the only time this has happened, and we got 4-5 inches of snow here, that is the conclusion I have come to.

So, is there a high chance of serious engine damage here, or did me turning of the engine and letting it cool down those times prevent the damage? Could the high readings be false highs because of snow clogging the fan since the temp gauge dropped almost immediately each time, or did it really get that hot? How well does the LT5 handle overheating? I am taking my Z to Marc in July for some other small, unrelated, issues, so he will look at it and let me know for certain, but I figured I can get some input from here and get some closure, hopefully.

pushrod-v8

How does the car drive?

90VetteZR-1

It has driven normally the entire time. I won't be able to drive it again until Sunday, so I will give an update then, but i didn't hear, feel, or notice anything not normal.

pappy.72

How is your water/coolant ratio. Could it have froze up? Happened to me once in my old Honda. Temp gauge shot up so I pulled over to check it out. Sure enough my resevoir was a slushy.

90VetteZR-1

I thought about that, but forgot to check it while I had the hood up. I will check Sunday, but it won't tell me anything about today's issue, unfortunately. I did watch for the coolant light to turn on, but ut never did, so i feel good about the coolant level, at least, but i dont know if its slushy. I flushed it last year and filled it with 50/50, so i assume it still 50/50. It got down to 7 degrees last night, but i thought that was above the freezing point for antifreeze.

Dynomite

50/50 antifreeze freezes at -35 deg F.

If you had a 50/50 mix of antifreeze and water the coolant would boil @ 265 degrees F with a 15 pound cap. The boiling point would raise to 270 degrees F if you had a 60% antifreeze mixture with a 15 pound cap. If you had a 70% mixture the boiling point would raise to 276 degrees F.

You might try this to get a handle on your analog gauge with digital feedback......

Hold button on each side of Fan symbol on Climate Control until 00 appears. Then tap button just to right of fan button until you get to 16 on the indicator. Tap center fan button again and you will see digital Coolant Temperatures in Deg C. You are shooting for 87 deg C to 100 deg C and maybe on real hot days......110 deg C (time to turn off AC). Actually time to turn off AC at anything over 100 deg C.

Somewhere as I recall......as long as you have coolant circulating and not boiling....you be OK but to not get into habit of getting that hot. So....were you really that hot......or not? Another recall is that as long as you did not blow a head gasket you be OK....but do not quote me on that one.

Did you observe Oil Temperature when the Coolant Temperature indicated approximately 260 deg F?

Marc Haibeck can certainly investigate this issue for you as well as determine why you temperature gauge is behaving with such inconsistency. If you did serious engine damage, the symptoms would include Coolant in Oil, Bubbling in coolant overflow container, Oil in coolant overflow container, Compression variations, Blue Smoke in Exhaust.....if nothing in these regards.....drive it but do talk with Marc since he will be working on your LT5.

Oh....and I got close to that temperature when my Water Pump Impeller Fell off/came loose of shaft. Now that is hard to diagnose for sure. No Harm and No Foul after replacing the Water Pump. And this was a New Water Pump.

One other item.....you say the temperature hit 260 F one half mile from house.....that is strange and I would suspect a stuck thermostat in that case. A sticky thermostat would give you the temperature inconsistency you describe. But only one half mile is still difficult for the temperature to rise that fast if you started out with cold engine.

I am sure several of us have experienced the sticky or stuck thermostat and some others may have reached the cross hatched area. They may share their experience and put your mind at ease having not blown their own engines

90VetteZR-1

I thought about a head gasket issue, so i will check that tomorrow before i start back home. There is no blue smoke, i will update tomorrow when i get ready to drive.

90VetteZR-1

Ok, so no water in the oil, no oil in the coolant. She drove fine on the trip home, never got close to the hash, and I drove a bit hard at point without issue. Thank you everyone for your answers to my questions I will continue to keep an eye on things.

Dynomite

Very interesting......I would get a new 180 deg Thermostat from Marc with rubber gasket and stick it in.....Marc has the best Thermostats.

I put Marc's 180 deg Thermostats in all Zs

XLR8TIN

Is the coolant level in the white overflow tank in headlight bucket staying at a normal level?

Zrxmax

I have had a couple of thermostat malfunctions in recent years that caused mild spikes in temps though not nearly as high as the ones you have had. It appears you will be looking at your thermostat also.

Dynomite

Let us know what happened as this is an interesting topic

phrogs

radiator cap, or overflow cap on our cars can cause overheating issues as well, Check it for cracks, and its the easiest part of the system to check and replace.

This happened on my Ferrari 308, expansion tank cap was cracked causing it to over heat.

Paul Workman

BTDT My overflow tank was over flowing, and temps were warmer than normal. I was thinking the worst (head gasket, as my primary fan crapped out once and it go hot), but Marc suggested testing the pressure cap, which I did. Bad cap! A new cap and all was well.

I have a scanner which reads the digital temp for me, but the procedure Cliff (Dynomite) listed will put a spotlight on things.

One more thing...check you coolant level. IF you are leaking somewhere, (other than head gasket, I mean), that too can cause temps to fluctuate as the water pump is "starving".

I bought a coolant system pressure tester at AutoZone. One of the nicest gadgets to have on hand for checking all my 7 vehicles , and it wasn't expensive.