Alternative coolants

Here's another one of those engineering things and also the four worst words you can say when working on a car: "While I'm in there"

Since every component of my cooling system is new, switching over to an alternative coolant from the classic green stuff would be easy to do. Now I'm not talking about running a waterless coolant or something like that, but we do have a rainbow assortment of coolants today aside from the green goo and Dex-kill. (Dex-kill is probably ok to use these days, to be fair... I'm pretty sure the issues that turn it into clay have been resolved by now.)

In looking at the compositions and test results it does appear to me that I could pick a coolant based on a color I like and it'd work just fine. I kind of like the idea of using the G40 Euro coolant so I'd have the same thing on hand for two different cars I own. Or maybe even the heavy duty diesel truck stuff since it's cheap at Walmart.

I am curious if anyone out there went with something other than classic green or Dex.

I will be interested in what others are doing also. I switched the RMW from Dex to GO5 as soon as I got it home, and I did our 07 3500 6.0L van as soon as it was out of warranty. Just looking at the rust gunk on the water pump when it did fail was enough for me to confirm the Dexcool is not good stuff. New vehicles and changed very regularly it may be OK, but no need to take the chance.

I also, though, do worry about using any of the organic acid mixes and not just the glycol plus some additives green stuff, though. Still haven't decided for sure what I will use when I have the fully new engine in place this spring. The van 6.0 is a iron block, aluminum heads, and it has been fine for 8 years with only one change of the GO5 which was still perfectly clean.

All the manufacturers use Dexcool as factory fill. Even the ones with ten year warranties. As with the Opti-spark, everything up to and including global cooling was blamed on it.

Used as directed, Dexcool is a superior coolant to the silicate based products it replaced.

I have heard that there have been a few other brands use Dexcool in some of their vehicles but I know for sure Honda and others don't as they have their own specific and almost always a different chemistry than Dexcool.

IIRC Dexcool is Organic Acid Technology and many of the others are Hybrid Organic Acid Technology which is what G05 is.

The hybrid combines an OAT with another technology that I don't recall the name of.

Dexcool has some issues with going too acid and causing some electrolytic issues by some accounts, and one of the tests of it to see if it is bad is to check it's conductivity.

From what I have read, the hybrids have not had the eating gaskets and sludging issues that Dexcool has in the past anyway.

Today's Dexcool is definitely not your parents' Dexcool. And that stopleak the marketing guys forced on the engineers to get that insanely long coolant change interval in 1996 didn't help. The throttle body on my '96 had the heater passages COMPLETELY CLOGGED.

That all said, I run Dexcool and distilled water in my B-bodies. I don't have a preferred brand.

I will be running a product called Thoroflush through both of my cars in the near future, and removing the (new, fresh) knock sensors to fully drain the block as part of that.

For the record, I also have several 03 Chrysler minivans that used G-05 as the factory fill. I run that in them as well. Interestingly, they have had zero clogging issues ever.

I'm not sure there will be much reactivity with the cast iron insides of the block. There was so much GM coolant sealer pellet residue in the motor it's almost like the inside is coated in brown rubber. Tanking the block didn't touch it. Parts washer didn't either. No chemical flush fazed it. That's some tough stuff.

Interesting on the sealer, has it been eliminated in the Dexcool now. They still claim very long life.

At least back a ways when the "sludging" was a big issue in the 4.3 and 5.7 pushrod V engines, there were a lot of the non GM experts saying a major part of it was a reaction between the Dexcool and the residual sand that had always been left in crevises of the block and head castings plus the iron in the block causing the thick pasty brown goop we all have seen. The old school blocks and processes were more likely to have residual sand in them. I found it on my knock sensors, and some very similar on the waterpump steel parts, but the block appeared to be very very clean inside when I disassembled it. Perhaps the GO5 helped clean it up a bit?

I had heard that too about the sand. I'm pretty sure any sand is probably perma-glued to the block with all that cooling system sealer. I also was under the impression that the major cause of Dex-sludge was due to bad pressure caps that were letting in more air than expected, which caused some sort of chemical reaction. Not sure if that was true but that was apparently GM's report on the issue.

lamune wrote:

I had heard that too about the sand. I'm pretty sure any sand is probably perma-glued to the block with all that cooling system sealer. I also was under the impression that the major cause of Dex-sludge was due to bad pressure caps that were letting in more air than expected, which caused some sort of chemical reaction. Not sure if that was true but that was apparently GM's report on the issue.

Having been there with 60s-70s blocks in my history (Mopar not GM), I can tell you that loose sand in blocks was common. We always had to remove it all before doing a block fill, up the freeze plug level, on the small block A engines to to get the filler to stick to the block right. If you didn't remove it, the filler didn't stick right and the 4 bolt main bolts that go into the water jacket would leak to the pan. I assume the GM blocks were similar.

The bad cap thing, I think is related to the oxygen needed to make the iron oxide rust sludge we have seen. I think the combo of sand, old coolant, and too much oxygen is the fatal combination of stuff that made for major failures. Of course the corrosive nature of the Dexcool on intake gaskets made all of it worse, especially the air in the system issue.

Almost all the major antifreeze brands went to anti-leak formulas back then and all of them quickly backed off after a couple of years because of plugged heater cores and radiators, so Dexcool is not alone in that F-up.

At this point, I really don't know which is best to use in any vehicle (except OEM in stock OEM vehicles except Dexcool). The Euro specs say no phosphates, Asia specs say to use phosphates, who knows what works best in an old Buick?

I am inclined to stay with the G05 in the Buick, but the phosphated Asian antifreezes are an impelling alternative to me. Deathcool is definitely out for me with all the past issues

I don't think any opinion is inherently wrong in this discussion.

booster wrote:

I don't think any well reasoned opinion is inherently wrong in this discussion.

Very few B-body owners actually pull the knock sensors and flush the block. For legitimate reasons, to be sure, due to limited access and delicate knock sensor housings. After pulling the engine in a '96 Impala I'm restoring, unscrewing the knock sensors and nothing coming out, and then having to chip through a solid layer of crap behind the opening, I'm confident that in the block is where all the junk hides. This is why B-body heater cores clog up regularly while no other vehicle I've ever owned has this problem.

sherlock9c1 wrote:

booster wrote:

I don't think any well reasoned opinion is inherently wrong in this discussion.

Very few B-body owners actually pull the knock sensors and flush the block. For legitimate reasons, to be sure, due to limited access and delicate knock sensor housings. After pulling the engine in a '96 Impala I'm restoring, unscrewing the knock sensors and nothing coming out, and then having to chip through a solid layer of crap behind the opening, I'm confident that in the block is where all the junk hides.  This is why B-body heater cores clog up regularly while no other vehicle I've ever owned has this problem.

That is a good point. Access is poor, but not horrible, at least on our 96 RMW, but it sure does make a mess when you pull them out and get a engine full of water in the face.

Some of this may be related to what you say, beyond the heater cores even. In these engines you only can change probably less the 50% of the coolant unless you pull the sensors or remove the thermostat and do a long feed and bleed though the radiator drain with the engine running. If Dexcool is not changed when it gets old you get sludge it appears, and if you only get 50% out you don't get the old out. Add some sand in the block and lots of iron parts and you get all kinds of bad stuff happening.

I had to poke through a layer of crud to drain the block on both LT1's I have worked on.

I'm going to try the red OAT coolant from Walmart that goes into big diesels. We'll see how that works out.

Here is a link to an article from 2004 that probably does a better job explaining stuff up to that date than most articles.

[You must be registered and logged in to see this link.]

Of particular interest was the emphasis on air in the systems causing rusting in the air trapped areas that eventually settles out somewhere like the block or heat exchangers, especially for Dexcool. From what I seen to hear, the LT1 design is very, very, prone to air inclusions and pockets?

One thing I keep forgetting to ask of this group who have seen a full range of LT1 engines. I think 1996 was the first year for Dexcool, so the earlier engines would have had conventional antifreeze in them I assume. Did those engines also exhibit sludge at the knock sensors like the Dexcool engines have?

booster wrote:

Here is a link to an article from 2004 that probably does a better job explaining stuff up to that date than most articles.

[You must be registered and logged in to see this link.]

Of particular interest was the emphasis on air in the systems causing rusting in the air trapped areas that eventually settles out somewhere like the block or heat exchangers, especially for Dexcool.  From what I seen to hear, the LT1 design is very, very, prone to air inclusions and pockets?

One thing I keep forgetting to ask of this group who have seen a full range of LT1 engines.  I think 1996 was the first year for Dexcool, so the earlier engines would have had conventional antifreeze in them I assume.  Did those engines also exhibit sludge at the knock sensors like the Dexcool engines have?

I bought a 94 wagon with 90K on it in 2008. Fleet maintained for first 50K by an aviation company, and then employee of said company had it for the next 40k.   It sat around the side of my house for about 5 years 2010-2015 when the fuel pump died (and I had 4 other wagons).  In 2015 I drug it out and started working on it for a t56 swap.   It still had 90K but I had run it regularly until the pump died.  

The engine was super clean inside as we pulled the valve covers, timing cover, and oil pan during the re-hab.

The coolant system looked like mud.   Flushed and flushed it, never got it all out as I ran straight water in it l(ive in south FL ) and dumped it 3 times in the 2K miles I put on it until it was totaled. was dumping it about every 600 miles to try and get it as clean as possible before I added coolant. Never got that far

Sprocket wrote:

booster wrote:

Here is a link to an article from 2004 that probably does a better job explaining stuff up to that date than most articles.

[You must be registered and logged in to see this link.]

Of particular interest was the emphasis on air in the systems causing rusting in the air trapped areas that eventually settles out somewhere like the block or heat exchangers, especially for Dexcool.  From what I seen to hear, the LT1 design is very, very, prone to air inclusions and pockets?

One thing I keep forgetting to ask of this group who have seen a full range of LT1 engines.  I think 1996 was the first year for Dexcool, so the earlier engines would have had conventional antifreeze in them I assume.  Did those engines also exhibit sludge at the knock sensors like the Dexcool engines have?

I bought a 94 wagon with 90K on it in 2008. Fleet maintained for first 50K by an aviation company, and then employee of said company had it for the next 40k.   It sat around the side of my house for about 5 years 2010-2015 when the fuel pump died (and I had 4 other wagons).  In 2015 I drug it out and started working on it for a t56 swap.   It still had 90K but I had run it regularly until the pump died.  

The engine was super clean inside as we pulled the valve covers, timing cover, and oil pan during the re-hab.

The coolant system looked like mud.   Flushed and flushed it, never got it all out as I ran straight water in it l(ive in south FL ) and dumped it 3 times in the 2K miles I put on it until it was totaled.  was dumping it about every 600 miles to try and get it as clean as possible before I added coolant.   Never got that far

That's very interesting, and I assume that one had regular green stuff in it? I was sort of expecting that answer, I think, as the more I look at it, the whole air in the system/rust seems to keep jumping the front. May be worse with Dexcool but maybe not, also. My 96 had obviously been acid cleaned before I got it as it had a new radiator, clean Dexcool, etc. It did still have some, but not plugged, sludge around the knock sensors when I pulled them to get rid of all the Deccool. Waterpump had some when it failed a couple of years later also. What is kind of interesting is that when I got rid of the Dex 7 years ago, I put in GO5 which is a HOAT chemistry. When I took my heads and block in to the shop for machining this winter, the owner looked at it commented on how clean the water jackets were compared to what he would normally see. This is a high end race shop, so he doesn't see crap maintenance stuff. Was it the previous cleanout or the GO5, I have no idea.

I've done some more research and here's the information I've compiled so far:

The classic green stuff has both phosphates and silicates in it as corrosion inhibitors. European coolants drop the phosphates due to their hard water reacting badly with phosphates, causing scale and corrosion. On the other hand, Japanese manufacturers drop the silicates as they react badly with the compounds in their seals, which causes them to fail.

So I feel confident in speculating that since the green stuff has both silicates and phosphates, you could use either a European or Japanese formulation in an older car since dropping one or the other probably won't have much of an impact.

Dexcool has some interesting history behind it. Wikipedia has a pretty good summary. One interesting data point is that it contains additives that are plasticizers and can attack nylon and silicone. That could possibly explain the one set of 9C1 silicone hoses I got that were disintegrating from the inside out. Given that silicone should be basically impervious to just about anything in a cooling loop I couldn't figure out what could possibly cause them to break down. In any case reading up on Dexcool and the various failure modes it has over even the classic green stuff would still prevent me from using it. If I did use it I'd be checking pH, color, etc quite frequently. If you keep up with it though it should be just fine.

In looking at the various options and data I've seen, the best thing to do would be to stick with the green stuff and change it every 2 years. It has the longest track record and with both the silicates and phosphates provides good corrosion protection. Again, as long as it's changed regularly before it turns into chocolate milk.

Of the OAT/HOAT coolants available I would go with the G05. It seems like the most cost-effective and compatible modern coolant which should work just fine in these older motors. The other formulations would likely not cause any problems either, but the reason those coolants are so formulated are for reasons that don't apply here. The seals we use are clearly not silicate-sensitive and using distilled water avoids the complications with phosphates. Obviously though without many people switching over we have no real long-term data to go on, so there is potential risk there.

One other thing I did notice is that the VW G13 stuff is made with glycerol. This was done to make manufacturing and disposal less problematic. If the stuff weren't so costly I think it'd be good to keep one coolant on hand that I can use in 2 cars... but the price of it makes that not worthwhile. Classic green is still the cheapest solution.

Most of the discussions I have seen on it seem to gravitate to two different issues, with the most popular on being the gasket eating characteristics of Dexcool. The other issue is the sludging which seems to get a lot less attention, but I think in our engines may be just as important.

The gasket failures seem to have been traced to the additive 2-DHA in the Dexcool, and apparently in many other extended life antifreeze brands. Some tout no 2-DHA, others don't say, and from what I read some have had it when they said they didn't. So kind of wild west type of information. G05 is said not to have and 2-DHA. It also appears the conventionals don't also, but unable to confirm for sure.

The sludging doesn't really seem to have much consensus or even decent information, at least that I have found yet. The previously mentioned sand issue is on that comes up, and the problem of air in the system in iron areas is probably an issue with any antifreeze unless it would hold any rust in solution which I think is unlikely.

I think I need to get a good look at the water passages in the waterpump and engine as I reassemble to see where air pockets could get trapped. I think the throttle body is the highest point on the engine and it doesn't have a bleeder so stuff like that may contribute. Our LQ4 6.0 engine in our Chevy van is iron block and aluminum heads and it has a continuously connected bleed line from the throttle body to radiator neck IIRC, but it also is a non pressurized tank system so not exactly same. Perhaps a full time line from the highest point back to the tank would help, as long as the level in the tank was the highest point of the system.

G05 is still looking like the top contender to me, but perhaps something will come up that is better.

I think it also is pretty essential to get the knock sensors out when you change the coolant so get all the old out and get a look for sludge.

one thing I did when changing the radiator and water pump on my 'new' 72K (at the time) wagon was to used my leaf blower and shoot it in the water pump openings. I was very surprised and how much liquid came out!

This has been an interesting thread, that's for sure. I happened to take a look in the garage and noticed that when I last filled the wagon, I used Prestone "Universal" coolant, and never really had any idea what that meant. It wasn't in there long enough to say whether it was harmful in any way, so no conclusion can be drawn there.

I also did notice that VW's G13 coolant (AKA "G40" coolant) is compatible with VW factory-fill coolants from 1980 forward, so from a component and metallurgical perspective it seems pretty similar enough to a 1990's GM motor that it should work just fine. Also it's purple, how cool is that, right?

One other thing I noticed when on the search for the green stuff. Of the 3 places I checked, one had no options there, and two had house-brand only... one of those only 50/50 which I don't like to buy since diluting it yourself is cheaper. I ordered Zerex from Amazon instead, that was the easiest thing to do.

I have enough G12/G40 and green stuff on hand that I could do either one. They both seem very broadly compatible.

I almost made a mistake and wanted to document it in case anyone else is following along. I decided to build myself some boy-racer silicone heater hoses and ditch the 20+ year old 9C1 hoses. I was set to use the VW G13 coolant but noticed that the silicone hose manufacturer specified to avoid using coolant with 2-EHA in it. Sure I know that Dex-Cool has that, but as it turns out, so does G13, G40, and a bunch of other coolants as well. So if you're going to run silicone hoses, stick with the old-school green stuff or go with G-05. (I'm going to try the G-05)

I also realize that the 1996 9C1 cars ran Dex-Cool with the silicone hoses and I haven't heard of any unusual horror stories about the hoses exploding, just the usual Dex-Complaints. (maybe it turns to clay long before the hoses fail?)

By the way the data I see here is not really clear: According to one silicone hose manufacturer, the OAT 2-EHA "fumes" will pass through the inner layers of the hose and attack the polyester mesh reinforcement which would cause the hose to burst.