C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Coolant issue and decisions

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Old Jul 13, 2025 | 11:03 AM
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Default Coolant issue and decisions

I have a coolant issue which is partly totally normal and partly unusual, to me at least.

The background is that I have a lower mileage 94 that I picked up a little over a year ago. When I was looking it over for the first time, I did check the coolant and it looked new. Never gave it a second thought though it was on my list to flush and replace. Fast forward to late last week where the car came close to, but didn’t quite overheat. The 115 temperature here may have contributed The oil temp stayed pretty much in the middle of the range so I wasn’t hugely concerned.

When I opened the rad cap, I was greeted with brown, silty looking coolant. I’m on my second fill and drain (distilled water) and it doesn’t look much better. While I’m convinced that when I looked the first time, the coolant was green and that there was a very slight green tinge to the silty water, I’m really not sure.

The problem: I’m just about to leave on a quick 1500 mile trip. There’s a 0.00% chance that I’ll see freezing temperatures but I’m still not enthusiastic about running just water. I’ll continue the flushes but doubt I’ll have the time to get it totally clean before I leave.

The question: Do I just do the trip with straight water and not worry about it? Assume that my vague recollection about green was correct and dump in a gallon of universal or go Dexcool like the General intended?

Thoughts?
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Old Jul 13, 2025 | 12:06 PM
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Originally Posted by CA-Legal-Vette
I have a coolant issue which is partly totally normal and partly unusual, to me at least.

The background is that I have a lower mileage 94 that I picked up a little over a year ago. When I was looking it over for the first time, I did check the coolant and it looked new. Never gave it a second thought though it was on my list to flush and replace. Fast forward to late last week where the car came close to, but didn’t quite overheat. The 115 temperature here may have contributed The oil temp stayed pretty much in the middle of the range so I wasn’t hugely concerned.

When I opened the rad cap, I was greeted with brown, silty looking coolant. I’m on my second fill and drain (distilled water) and it doesn’t look much better. While I’m convinced that when I looked the first time, the coolant was green and that there was a very slight green tinge to the silty water, I’m really not sure.

The problem: I’m just about to leave on a quick 1500 mile trip. There’s a 0.00% chance that I’ll see freezing temperatures but I’m still not enthusiastic about running just water. I’ll continue the flushes but doubt I’ll have the time to get it totally clean before I leave.

The question: Do I just do the trip with straight water and not worry about it? Assume that my vague recollection about green was correct and dump in a gallon of universal or go Dexcool like the General intended?

Thoughts?
your car didn't come with Dexcool
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Old Jul 13, 2025 | 12:36 PM
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Originally Posted by Cruisinfanatic
your car didn't come with Dexcool
Are you sure? Searches on here seem to indicate otherwise.
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Old Jul 13, 2025 | 12:56 PM
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Dexcool was first used in 96 models. Coolant is there for anti corrosion and lubrication, not just for a lower freezing point. Water alone cools just fine. I wouldn't drive long with straight water.
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Old Jul 13, 2025 | 01:01 PM
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It’s the lubrication part that I was most concerned with though corrosion is a consideration too.
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Old Jul 13, 2025 | 01:22 PM
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Originally Posted by CA-Legal-Vette
Are you sure? Searches on here seem to indicate otherwise.
how about I google it for you
https://www.google.com/search?client...ool+first+used
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Old Jul 13, 2025 | 01:56 PM
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I did and found links to Dexcool as well as the general statement that said the General didn’t switch to Dexcool until 96.

In any case, I did it the hard way. The Servical manual calls for spec 1825M which equates to old, green coolant. Thanks both. Without that ambiguity, I’ll clean it as well as time permits and dump a gallon of Prestone universal in. I don’t mind wasting that. Just didn’t want to end up with a rad full of gooey chunks.
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Old Jul 13, 2025 | 02:13 PM
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With any coolant issues, we should always do a leak check and cap check.

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