randog

About a week ago during easy city driving my Z boiled over. Coolant spewing out the overflow. Called a flatbed and towed it to the dealer. They said it was a faulty rad cap. Drove it home easy about 20 miles. Seemed fine. Coolant at about 180. Yesterday was driving around some city some freeway taking it easy. Coolant also around 180. Put on about 50 miles and just pulling up to my house it boiled over again. It started to climb to about 200 during the last few miles. Coolant reached 235 fan kicked on. It didn't seem to be cooling down so I shut it off. It's going back to the dealer on Monday. Anyone else had this issue?

JoesC5

I question the accuracy of your temp gauge. 180 is way to low a reading once the car is warmed up. I believe most C7's run around 205 to 210. I doubt if a Z06 runs less than that.

That doesn't explain why you are boiling over, but the dealer should take a look at the accuracy of the temp gage when they are trying to solve your overheating problem.

randog

Good point. Thanks!

BTCorvette

This information does not sound right ... No new Corvette ever run a normal driving temperature of 180 , this whole incident about what you are describing about how your corvette is over heating after you took it to be Service sounds like joke.,,
April Fool is over.,,, besides that every new corvette have a normal driving temperature of about 200 to 210 degree

randog

It's no joke. Outside temp was only 45 or so. If that makes a difference.

mdz06vetter

You have to have something restricting proper coolant flow. As mentioned at "normal operating" temperature after car has properly warmed up your gauge should be reading at a minimum right around 200. I would be checking with a different dealer if all they have said the problem was a faulty radiator cap.

FirehawkTA

So the fan definitely kicked on at 235 and then the temps continued to climb?
Shouldn't the fan come on sooner than that? Anyone know, does the Corvette have 2-stage radiator fans?

l888apex

Maybe an issue with the thermostat not opening?

stevebz06

If it was a bad radiator cap, maybe they didn't completely bleed out all of the air in the cooling system when they refilled it. I incorrectly refilled my LS6's cooling system after draining and got the boil over situation with normal temperatures showing on the instrument panel.

If that isn't it, then I would look for a stuck thermostat. If that isn't it, then you might have an gasket problem. Check and see what the engine oil looks like.

mdz06vetter

What Steve said.................

randog

They tested the rad cap and said it would only hold 2 psi, so I guess it was a bad cap, but there must be more going on. When I first got the car, with only 5 miles on it, it steamed out a bit on the first few miles, but then quit. I just washed it, so I thought it must have had a bit of water on the engine, and I didn't smell any antifreeze, so I thought it was no big deal. And it never did it again until it had about 350 miles on it. I guess they will figure it out, it seems weird it would spew coolant out at 210 to 220.

randog

Yeah, I thought about the thermostat too, hopefully that's it. The oil looked good on the first boil over, and they just changed it and it looks ok now as well.

randog

The dealer said the fan is supposed to kick in at 235 which it did. When I pulled up to my shop, the coolant was about 220, and it was spewing out the overflow, so I shut it off, and it climbed to 235 with the engine off and and fan running. Then it slowly cooled of course.

avalonandl

These cooling systems are DESIGNED to run under pressure and 205-210 is normal and needed for emissions. Fans kicking on at 235 sounds normal and these engines aren't really overheating until over 235.

A Rad cap needs to hold at least 15 psi.

randog

It sure does sound like a thermostat issue. As I mentioned, it was hovering around 180 for quite a while, but it was a cool day and I was going slow, so maybe that's why it didn't reach 205 of whatever normal is until later in the day, not sure. I was supposed to travel to BC with it this weekend, but our dog is sick, so we postponed, good thing it would have sucked breaking down on the road.

jim2527

Are you topping off the over flow tank when the cars cooled off? Is there any coolant in the tank?

randog

When I got it back from the first boil over, I checked the level in the tank and it was about 1" from the top of the tank. I actually stopped at another dealer during the second boil over as it happened right in front of their door, and they said it was probably just overfilled. Very frustrating, hopefully it's something minor, at least the temp. never got up to anywhere close to the red line.

Movie Muscle

The rad cap is essential. If the cap doesn't hold pressure it causes the cooling system to boil over sooner. For every pound of pressure it raises the boiling temp. Coolant is a mix as we know. Here is a link to a great set of table explaining the relationships of pressure, coolant percentages etc.

Also the above poster is correct that an air pocket due to improper filling can cause issues. Have seen the temp gauge on my old vortec dually go mental due to air pocket in the cooling system. A little infrared temperature gun can verify things for you quick as far as temperature readings.

https://durathermfluids.com/pdf/tech...ling-point.pdf

randog

Thanks for all your advice gentlemen! Flatbed coming Monday morning to the dealer. I don't want to take any chances. Love that damn thing.

johnglenntwo

It can plague havoc on things. Ask them to check a few plugs next time. The plugs will be all over the place if this is the problem! A big problem that is easy to fix.