Dexcool vs. other coolants
I am still hearing Duramax owners discussing the Dexcool issue. I know GM insists it must be used. Is there any definitive information as to the advantages/disadvantages of changing from Dexcool to another brand of coolant/antifreeze? I am aware of previous lawsuits etc., but by now there must be expert guidance on this question. THANKS!
Texaco/Havoline Dex-Cool - reprint from 2003
Texaco/Havoline Dex-Cool
By TheDieselPage.com - 2003
GM made the switch to the new orange-colored Texaco/Havoline Dex-Cool in the 1996 model year due to its longer service cycle, longer water pump seal life, high temperature aluminum protection, and a higher coefficient of heat transfer. At the time of introduction, this new coolant came with a recommended 100,000 mile maintenance cycle. Shortly thereafter, GM began recommending a 5 year/150,000 mile coolant maintenance cycle for the 6.5L (and Duramax 6600) turbo diesel engines because of the improved long-life characteristics offered by this new coolant. According to a 1998 NARSA (National Automotive Radiator Service Association) report, Texaco/Havoline began recommending the average cycle life of this new silicate-free orange coolant be increased to 250,000 miles and beyond in other applications.
DEXCOOL is a registered trademark of General Motors Corporation, used under license by Texaco Lubricants NA. Dex-Cool contains an ethylene glycol base along with carboxylate corrosion inhibitors (organic acid) for an advertised improvement in rust and corrosion protection. For more information about Dex-Cool, you can call 1-800-782-7852 or visit www.Havoline.com on the web.
Conventional coolant, such as Prestone brand antifreeze/coolant shown above (green dye) is also an ethylene glycol based coolant, but uses a blend of silicate corrosion inhibitors. Green-dyed silicated coolants represent the type of formulation used by GM prior to the introduction of Dex-Cool. For continued cooling system protection, Prestone recommends an annual flush and fill when using a silicated ethylene glycol coolant. This is necessary because the concentration of conventional rust and corrosion inhibitors (silicates) tend to decrease over time. Prestone also produces a silicate-free organic-acid based coolant, but we have no experience with this product. For more information about Prestone brand automotive coolants, you can visit them on the web at www.Prestone.com.
GM does not recommend installing an organic-acid based coolant in systems with a copper/brass/soldered radiator because of a potential for lead corrosion. However, Prestone says their organic-acid ethylene glycol tests have shown no problem with lead corrosion, and recommends the use of their organic-acid ethylene glycol coolant in either copper/brass or aluminum systems. Our tests here at The Diesel Page with Texaco/Havoline Dex-Cool and copper/brass/soldered radiators have shown no internal cooling system deterioration after nearly 120,000 miles and four years of use (6.5TD).
Converting a system containing silicated coolant (yellow/green dye) to an organic-acid coolant (orange dye) requires a thorough system flush to remove all traces of the original silicated ethylene glycol coolant. These two coolants are somewhat compatible, in that you won't damage your engine or cooling system with a mix, but mixing coolants containing carboxylate and silicate corrosion inhibitors will shorten the service cycle to that of silicated ethylene glycol. Copyright 2003 by The Diesel Page
While Texaco/Havoline recommends a "good quality tap water" when preparing a 50% Dex-Cool solution, both NARSA and The Diesel Page recommend using distilled water to dilute Dex-Cool. Chlorinated or hard water can affect the long-life properties and corrosion protection offered by any automotive coolant.
However, mixing two unrelated formulations of organic-acid ethylene glycol coolants is a concern. There are several different chemistries used for long-life coolant that can appear as pink or orange or red. They may not be compatible with one another. Europe has their own formulation, Japan has theirs, Chrysler Corporation has theirs, and Texaco/Havoline has theirs. If someone topped off a 6.5 or Duramax cooling system with a non-compatible coolant, undesirable consequences could result. If in doubt, look for a description on the bottle indicating that it meets specification GM-6277M or ASTM D-3306. I always carry a gallon of pre-mixed Texaco/Havoline Dex-Cool (with 50% distilled water) with me whenever I travel, to help mitigate this possibility.
We have learned that an air/coolant interface within the engine or cooling system could create an environment for aluminum or iron corrosion when using Dex-Cool. Not coincidentally, GM incorporated an air-bleed screw in the 6.5L & Duramax 6600 thermostat housing. This provides a means to vent air from the cooling system. Additionally, the coolant surge tank is also designed to remove air from the cooling system. So, unless there is some sort of engine or cooling system failure (or inadequate initial fill), there should never be an air/coolant interface in your 6.5 or Duramax cooling system.
A recent class-action suit has been brought against GM for cooling system corrosion involving 4.3L engines used in GM's late model Blazer, Jimmy, Olds Bravada, Sonoma, and S10 pickups. As reported in the May 22, 2003 issue of The Columbus Dispatch, GM stated that it "is aware of concerns about Dex-Cool. However, those problems involve customers who ran their cooling systems for an "extended period of time" -- 15,000-20,000 miles - with low coolant levels." GM went on to say that "There are 35 million to 40 million GM vehicles on the road that use Dex-Cool, and the overwhelming majority have experienced no problems with the cooling system." As stated earlier, we have also identified a problem with a coolant/air interface, and the potential for corrosion as a result. We also know that cooling system performance (when properly filled with a 50% Dex-Cool/distilled water solution) will surpass those using a green silicated ethylene glycol coolant.
As a result of this class-action suit, some owners of the GM full-size diesel pickup engines have become concerned about the possibility of cooling system corrosion in their own vehicles. Ensuring the absence of air in your cooling system should preclude any sort of corrosion problem. If you notice the coolant surge tank level rising or falling beyond the hot/cold levels, you may need to investigate the cause. An external coolant leak, a faulty cooling system pressure cap, a leaking head gasket or some other sort of failure could cause an air/coolant interface to develop inside your engine. This is a bad thing.
Some have suggested draining the Dex-Cool and refilling with a green ethylene glycol coolant. Before taking that step, consider this: This radiator core image illustrates the result of improper cooling system maintenance after the vehicle accumulated just 135,000 miles. Perhaps more importantly, it also shows what the combination of improper maintenance and green silicated ethylene glycol can produce.
Human nature being what it is, too many people will neglect certain systems in their vehicle. The radiator shown here, the engine and the cooling system were replaced soon after that photo was taken in 1998, and the new cooling system and 6.5TD engine have subsequently accumulated 120,000 miles on a single initial fill of Texaco/Havoline Dex-Cool (& 50% distilled water). The internal condition of the radiator and thermostat housing still appear like new. If the Dex-Cool filled systems survive better when neglected, that's a good case all on its own to use Dex.
Some have blamed cylinder head gasket failures on Dex-Cool. However, here at The Diesel Page, we know that the primary problem with 6.5 head gaskets is directly related to the factory 21.5:1 compression ratio. During the 2001 Rendezvous in Ohio, Matt Koning, CEO of Peninsular Diesel told our group during a seminar that Peninsular had never replaced a failed head gasket on any of their 18:1 compression ratio marine 6.5L engines - not a single one in 10 years of 6.5 marine engine production. In contrast, head gasket replacement for the "on-road" 6.5TD engines (with their 21.5:1 compression ratio) is a somewhat routine occurrence between 80,000 and 200,000 miles.
There is no discernable difference in 6.5 head gasket reliability for engines built prior to or since the introduction of Texaco/Havoline Dex-Cool. If Dex-Cool created an endemic cooling system corrosion problem with the 6.5 and Duramax engines, The Diesel Page would be well versed in the science and chemistry behind it (by the shear volume of routine email messages and phone calls). Since The Diesel Page began in early 1996, a question about coolant type has not been an issue we've dealt with till this article.
Continued next post:
Copyright 2003 by TheDieselPage.com
DexCool in Detroit 8.2L Fuel Pincher
I'm very happy to have found this forum. Perhaps I can finally get some answers or at least advice.
I have a vintage 1972 Newell motorhome which was repowered in 1981 with a Detroit 8.2L Fuel Pincher turbo diesel. This is my first diesel engine. As of today this 33 year old engine has about 60,000 miles on it. I've done some research on this engine and it is known for blowing head gaskets. This would be really unfortunate since in the last year I haven't been able to find anyone with the tools to set the mechanical injector heights should we have to pull a head. Many other forums get nasty to people who have questions about this engine so I politely ask that I not be told to dump this engine in a lake....it runs great, has low mileage and with proper care I expect it to continue running for my lifetime since I can't see putting another 50k on a motorhome.
When I purchased it last year it had some very old coolant in it. Everything was rusty so we flushed it and put in some of the pink Diesel coolant we got from Advance Auto Parts. Shortly thereafter the radiator sprung a leak so I had it re-cored, changed all the hoses, new thermostats, flushed and refilled the cooling system with new coolant (again the pink stuff).
I have years of experience using DexCool in my vintage gasoline engines and LOVE it. I change it every 4 years and my cooling systems look like new. I've never discovered any corrosion issues when using DexCool. I'd like to use it in my Detroit, but any Diesel mechanic I talk to (besides telling me to change engines) says to use the pink stuff. I'm not convinced that this coolant is anything but expensive window cleaning solution and I'm worried that additional corrosion will compromise the head gaskets in my engine.
I've contacted Detroit and they sent me to Diamler who in turn sent me to MTU who in turn sent me back to Diamler who said they don't have any engineers left familiar with the 8.2.
Does anyone know if I can I use DexCool as a coolant in my Detroit? What are the risks?
Thank you very much!
Bob Kopicki
1972 Newell Motorhome with 1981 Detroit 8.2L Turbo
1976 GMC C1500
1967 Triumph TR-4a