: How to know if the coolant is old



weister42
02-21-07, 05:18 PM
Even though the coolant lasts 100,000 miles I'm a bit skeptical, so just in case how do I check the coolant and see if it's still good? I believe I have the green stuff in the system because the deposits around the tank is green.

Ranger
02-21-07, 05:35 PM
Not sure if there is a way to test it. You cannot go by color on an aluminum engine like you can on a cast iron one. Just change it if it is over 2 yrs/24K on a pre '96 (green) or 5 yrs/100K on a 96+ (Dex), or sooner.

BodybyFisher
02-21-07, 05:52 PM
If you think someone used GREEN in your 98, you need to follow the 2 year/24,000 mile change schedule.....as the corrosion protection on GREEN only lasts that long... You can use DEXCOOL but IF green was EVER used you must use the 2 year / 24K mile schedule..

eldorado1
02-21-07, 07:31 PM
I would use the 2 year/24k schedule on dexcool anyways.

Got a system full of red mud to prove it.

Ranger
02-21-07, 08:18 PM
Red mud? That has to be cooling system suppliment.

eldorado1
02-21-07, 10:05 PM
No, it was decomposing dexcool. The sheer volume would be impossible to get with any supplement.

One theory is that air gets in contact with the dexcool... another is that a hot spot just causes it to decompose. Google "dexcool mud".

Ranger
02-21-07, 10:11 PM
Don't believe everything you read on the internet. How does a liquid decompose? Both sound like Dex myths to me and neither makes any sense.

EDIT: OK you got me to do it. All those stories are from guys with cast iron engines and poor maintenance. Green silicated coolant plates the water jacket with silicates so when it gets low, the system will not oxidize. Dex has no silicates, so when it gets low the dry parts (usually intake manifolds) oxidize. Then the engine gets started, the coolant sloshes through the engine and washes the rust particles through the engine where they settle out in the radiator and Dex gets the blame. It's not air in contact with Dex. It's air in contact with cast iron (poor maintenance). As far as hot spots go, come on. Stop and think about that for a minute. A product that is intended to work hot turns to mud when it gets hot. If either of those to myths where true, we'd all have mud in our systems don't you think? Yet we hear none of that here.

weister42
02-21-07, 10:37 PM
I have a 98 so am I supposed to have Dex instead of the green? Also, I really don't know how old the coolant is, all I know it I bought the car from a GM dealership used without warranty and I've put 25,000 miles on it since. My highway coolant temperature is usually around 196~199 degrees, and it doesn't go any higher than 228 degrees in the cities.

Ranger
02-21-07, 10:38 PM
Yes, you are supposed to have Dex. When in doubt, change it.

eldorado1
02-21-07, 11:29 PM
EDIT: OK you got me to do it. All those stories are from guys with cast iron engines and poor maintenance. Green silicated coolant plates the water jacket with silicates so when it gets low, the system will not oxidize. Dex has no silicates, so when it gets low the dry parts (usually intake manifolds) oxidize. Then the engine gets started, the coolant sloshes through the engine and washes the rust particles through the engine where they settle out in the radiator and Dex gets the blame. It's not air in contact with Dex. It's air in contact with cast iron (poor maintenance). As far as hot spots go, come on. Stop and think about that for a minute. A product that is intended to work hot turns to mud when it gets hot. If either of those to myths where true, we'd all have mud in our systems don't you think? Yet we hear none of that here.

I can buy that. I can also buy it's rust.

But it's happening to properly maintained systems. Never low, always topped up.

When coolant circulates, it isn't always 210 degrees. The cooling jacket isn't at the coolant temperature either. Look up nucleate boiling.

Either the coolant itself breaks down, or it causes rusting. Maybe it's a galvanic reaction... who knows. I'm not a chemist, nor do I play one on TV. All I know is that dexcool doesn't last as long as GM claims it does.

http://www.consumeraffairs.com/news04/2006/08/gm_dexcool.html

Ranger
02-22-07, 12:34 AM
Either the coolant itself breaks down, or it causes rusting.
Well I think we can rule out causing rust as our engines are all aluminum and as we all know, aluminum does not rust. When I bought my '97 Deville I think it was 6 years old before I got to change the coolant :hide:. It had no "mud". According to the link you posted, I should have. How do we explain that? My wifes '96 Bonneville has over 135K on it and no cooling system problems. How do I explain that? I don't doubt that something is going on and there must be a common denominator some place, but I don't think that the Northstars have it. If GM knows something, they ain't talking and it may be like the Kennedy assassination. We may never know.

BodybyFisher
02-22-07, 07:23 AM
I have no problems with it in my 96 Deville, but I would NEVER use it in a cast iron engine....

res1n9k9
03-04-07, 11:02 PM
I have a 98, w/Northstar engine, and have been noticing the coolant temp creeps up at low speeds and up hills in the summer time with A/C on or off..above 222, the overheat I-light doesn't come on, so assuming everything is OK, but not use to these higher temps. It has about 30K on it now and suspect the coolant hasn't been changed, so plan on doing that...any recommendation on a flush treatment? Also another forum topic talked about GM pellets that are added to coolant...what are these please. I don't have my tech manuals yet, recommendation on where to buy, etc.

Ranger
03-05-07, 08:39 AM
No need to flush. Just drain & refill with 50/50 Dex & distilled water. You can get the tabs from any GM dealer or Walmart and such. Get Barsleaks tabs (product code HDC) or 2 tubes of the powdered version (G12BP). Put them in the radiator hose, NOT in the surge tank.

Guyz1996deville
03-05-07, 12:47 PM
when in doubt change it out. It is cheaper than over heating and cooking your head gasket...

wsolman
03-05-07, 12:47 PM
I would think that it's more of a pain than it's worth trying to figure out how old the coolant is. If you don't know, just change it. Then you know. It's cheap insurance. When I bought my 95 STS, the first things I did were change the oil and coolant.

clarkz71
03-05-07, 12:51 PM
When I bought my 95 STS, the first things I did were change the oil and coolant.


Same here.