Orange or Green Coolant for 1991 Chevy K1500 Pickup with 4.3 V6

Hello everyone,
About 7 years ago I flushed out the green coolant in my 1991 Chevy K1500 pickup with a 4.3 V6. The truck now has about 97,000 miles on
it. Normally, I would say stick with whatever coolant came from the factory but the orange coolant seemed like a better choice at the time. I liked the fact that it had a 5 year or 100,000 mile life, and the container said that it was easier on water pumps. It was also ethelyne glycole based and seemed to be very similar to the green coolant so I figured why not try it. After flushing the green coolant out, I replaced it with the orange coolant (I think it was texaco) and mixed with distilled water.
My water pump recently started leaking, I don't think it was the orange coolant, just age. I have not had any other problems with the cooling system, but I have recently heard some bad stories about the orange coolant causing head gasket damage, intake gasket damage, and water pump damage, on some vehicles. I've also heard stories about the orange coolant "sludging up" but I have not noticed that problem yet. On the back of dexcool containers, it says the coolant is for use with 1994 or newer vehicles and that on some vehicles (mine was not listed) if you did not change the coolant at least every 2 years, cooling system damage could result.
I'm going to flush the system & replace the water pump, upper and lower radiator hoses, thermostat, and radiator cap. Should I keep using the orange coolant or go back to the green coolant ? I would stay with the orange if I new it would not hurt anything, otherwise in the absence of an answer, I am inclined to go back to the green stuff, providing it won't do more harm than good.
I'm not sure why GM specifies 1994 or newer vehicles and I tend to wonder what the difference would be between a 1994 4.3 V6 & a 1991 4.3 V6 ? Are the seals or metals used different ? That's about the only think I could think of that would make a difference.
Is there anyone out there from a GM service department that knows the answer ? I'm hoping a mechanic or GM tech may be able to answer this question with a reasonable degree of certainty.
Thanks for your help. John
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I've taken all my orange coolant out and replaced with the green. There are too many problems with the orange coolant, why take chances.

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Although we have several people here who are professionals and who work for dealerships, finding the "answer" is a little more difficult.
I am a chemist and have worked in research and service for years, until my retirement in December 2006.
I have personally tested products like Dexcool under laboratory conditions and, of course, have followed the products to field applications as coolants.
The original "green" formulations were pretty good for most applications. They were all based on ethylene glycol in the early days, and the corrosion inhibitor packages contained materials to protect iron or steel, solder, brass and aluminum. (These are the same basic metals that are still used in automobile cooling system construction).
The biggest problems with the older green formulas were - (1) silicates, used to protect aluminum and its alloys, could precipitate under some conditions and form glassy deposits in the radiator and other parts of the engine, and (2) some of the components of the package were not deemed environmentally friendly by authorities in some countries.
The silicate problem was not always seen, and could be avoided by using quality products, decent water for dilution and reasonable maintenance.
Later, propylene glycol began to be used instead of ethylene glycol because it is a good bit less toxic than ethylene glycol. It is somewhat more expensive than EG and is somewhat less effective as an antifreeze, but overall not a bad choice.
The Dexcool type formulations were based on Organic Acid Technology, or OAT. Early patents by the Japanese were the first examples of this that I have seen. They were environmentally better than "green", but had some limitations. First, they had no long term inhibitor especially for aluminum (and we all know that aluminum is used more and more in modern vehicles to save weight and cost).
HOAT was developed to try to improve performance versus aluminum. HOAT contained some silicate components, at decreased concentrations usually, to give both protection AND to try to minimize the accumulation of silica deposits in the engine.
Bottom line... You pay your money and take your pick. AFAIK, there is no basic difference in the metallic materials used in engines now versus 10-15 years ago. We may be getting more aluminum now and less brass, but the basic compositions are similar.
If your warranty depends upon the coolant you use, then keep your warranty.
No matter what you use, it is wise, IMO, to flush out the cooling system every 2-3 years and replace with new fresh coolant. Corrosion inhibitor packages do not last forever. They degrade due to shear, hydrolysis, oxidation, and adsorption onto particulates. Even the glycols can oxidize with time, if you have any contact of the fluid with air. And, although that contact is minimized with the expansion tank systems now used, it will eventually take its toll. When you oxidize ethylene glycol, you get a mix of compounds related to glycolic acid and oxalic acids.
I probably have used more bandwidth than necessary, and I am sure some will have other points of view, but these are the facts as far as I have personally tested the products.
I am no great fan of Dexcool, but it does NOT destroy head gaskets. That was a myth.
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Agreed, nor did it cause the intake gaskets to fail. BTW, nice job on you reply.

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Sludging was due to the type of rad cap.
More info here,
http://www.imcool.com/articles/antifreeze-coolant/dexcool-macs2001.htm
http://www.imcool.com/articles/antifreeze-coolant/dexcool-johnbrunner.htm
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Snip Snip

I have an interesting question and I would like your opinion since you are a chemist. I just picked up at the beginning of February a 2003 X-Type Jaguar from a littlie old lady ( for real she is a relative) that had 3200 miles on it. It now has 4700 miles. I changed the oil immediately but decided to keep the factory coolant since it looks perfectly clean and had no major exposure to usage. The owners manual claims the coolant is good for five (5) years or 156,000 miles which ever comes first.
In your opinion based upon your knowledge of chemistry and your practical experience is there any likelihood of causing damage by not changing the coolant.
Thanks Double Tap
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Hi everyone,
Thanks for all your replies, especially HLS, I appreciate your detailed answer, and the fact that you are a chemist. If the orange coolant won't hurt my gaskets or seals, I will probably stick with it since I have had it in there for 7 years and everything seems OK. However, my feeling is that it's probably not all it's cracked up to be. Are the majority of new cars using the Orange Coolant now ? Are they likely to do away with the green coolant altogether ?
When I flush, I usually just take the old thermostat out, and then circulate distilled water through the system without the thermostat, drain, refill, flush again, and keep going until the water is clean. I keep the heater on hot the whole time. When I am finished flushing and I refill with new anti-freeze, I use distilled water to mix with the anti-freeze. I usually go ahead and replace the hoses, thermostat, & radiator cap at the same time.
Do you recommend adding a bottle of Chemical flush to the water on the first flush, to help clean scale, or should I just stick to using plain water to flush ? I would guess the chemical flush additive is compatible with the orange coolants. I have always wondered if the "chemical flush" might actually do more harm than good.
Lastly, is the orange Dexcool anti-freeze the same as the Orange Texaco anti-freeze I have been using ?
Thanks again guys, John
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Are the majority of new cars using the Orange Coolant now ? Are

I believe the majority of cars have now gone over to OAT or HOAT technology. It is a belief, not a known fact. \ There are a lot of cars on the road that have thrived on the older "green" fluids, and I don't foresee their immediate demise, BUT there are lots of new fluids on the market that claim to be compatible with anything.
And they may be.
This may be the path toward eliminating the green fluids (which are commodity priced....little profit), and going to something with a little more profit.

Except for very dirty systems, I see little to be gained by adding a flush chemical.. If you flush exhaustively to clean water, that is usually pretty good.
In some cases where you have a lot of oily scum or iron, it might be worth the effort.
Notice that no additive that you can buy at your FLAPS will help if you have silicate deposition in your radiator. Silicate is like glass, and nothing you can buy will dissolve it. It has to be rodded out, or cleaned with industrial strength chemicals.

I am not totally sure about this. I have heard that Dexcool is a license from Texaco, but cannot confirm this without researching it a bit.
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,000 miles which ever comes first.

I believe that since the mileage seems to be quite low, AND since your coolant is clear and without indication of corrosion by-products, you are probably good to go for a while.
When you start seeing scum, solids, iron rust, etc in the coolant, that is a pretty good indication that you have problems building.
Breakdown of the corrosion inhibitor package depends on time, temperature, oxygen contamination, and circulation (shear).
In your case, which is a bit unusual, it would seem that you have not challenged the integrity of the coolant yet.
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Thanks for the input. Your opinion confirms what I am thinking. Double Tap
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PMFJI, but what's your opinion on the "universal" stuff vs. straight orange/green? I find it interesting the universal stuff tends to have a greenish color ;)
-GV
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snipped-for-privacy@nospam.nix wrote:

(snip)
Wow! Very nice anti-freeze summary. Thank for that post.
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There has been quite a lot said about incompatibility between at least some of the Dexcool formulations and certain plastic seals. Personally I would take you car back to green, which is actually getting harder to find. For example, standard Prestone is now a formulation similar to Dexcool and not at all like the old standards. Peak still offers a conventional green coolant as do a few others.
John
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Hello everyone
One last question, is water pump lubricant worthwhile, & is it compatible with the orange coolant ? I have not used it but know some people that recommend it.
Thanks John
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