Save me the effort of researching this one. Does anyone know when GM started requiring DEX-COOL in Corvettes? I know it was after 1992 but I believe it was prior to the 1996 model year, the end of C4 production.
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In Appreciation of John Hinckley -
Re: When did the DEX-COOLRrequirement Begin
All 1996 model year GM car and light trucks except Saturn, which switched a year or two later, so the last C4 year would have been Dexcool.
Duke -
Re: When did the DEX-COOLRrequirement Begin
Duke-----
Thanks. The cooling systems in 1992-96 Corvettes with LT1 and LT4 were basically identical. So, by "extrapolation" Dex-Cool should be OK for, at least 92-95 as well as 96.
As a matter of fact, I used Dex Cool in my 1992 the last time I replaced the coolant. I just drained it today and there was not even a hint of any rust or corrosion. Absolutely no sludge or any other "precipitate", either. The coolant looked just about the same as the day I put it in. So, I'm going back in with Dex Cool.In Appreciation of John HinckleyComment
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Re: When did the DEX-COOLRrequirement Begin
Do not know about earlier years, however in my 1996 Corvette owners manual and also in my 1996 Monte Carlo owners manual specifies in doing a coolant change to use a supplement installed with new DEX-COOL and preferably distilled water. The supplement is GM Part No. 3634621. The supplement is 6 tablets. In doing a coolant change in my 1996 Corvette I also remove both knock sensors to drain the block in doing a coolant change.Comment
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Re: When did the DEX-COOLRrequirement Begin
I think those tablets are to prevent small leaks - same thing as Bar's Leaks tablets. One of the things I noticed about Dexcool it that it has more tendency to form small leaks - for instance at hose connections.
This makes sense because Dexcool has an OAT corrosion inhibitor package, so there are no salts that can precipitate out to plug tiny leak paths.
Joe - when Dexcool came out I was a big proponent and switched all my cars to it, but I now just use Dexcool in my '91 MR2. I talked to Texaco since they offered a commercial version that could be bought at sources other than GM dealers. They said that Dexcool has a tendency to leech lead out of solder, but it was primarily a disposal issue, however, if it leeches lead at some point solder joint integrity might be compromised, so there was a concern in the back of my mind.
When Zerex G-05 was introduced I switched my vintage Corvette recommendation to G-05 as it is a HOAT type and effectively the new "universal" antifreeze. It meets GM-1899M, which is the antifreeze spec for pre-'96 GM vehicles. The G-05 HOAT formulation was developed by BASF and Mercedes has used it since the mid-eighties. After the DB-Chrysler merger Chrysler cars swtiched and ultimately Ford also choose the formulation for their new vehicles.
Despite all the publicity about Dexcool "sludging" I never had any problems with it, but if one knows for sure that the cooling system has any soldered components, I think G-05 is a better choice. Modern cars typically have aluminum radiators and heater cores with crimped-on plastic tanks, so there is no solder in modern cooling systems.
Toyota and most of the other Japanese OEMs use an OAT, but it's a different formulation than Dexcool, which has a component that they don't like, saying it is a "plasticizer" that can effect hoses and plastic components.
Along this line Honda was very upset when GM specified Dexcool in an engine that Saturn sourced from Honda. Apparently Honda failed to address the issue during contract negotiations. GM refused to modify the contract, but I'm sure if GM had any concerns they would have addressed them in some way.
Engineers don't always agree on solutions, and often there are mulitple ways to skin the cat. If you look at the Valvoline Web site, you will find that there are five or six different ethylene glycol-based antifreeze products that have different corrosion inhibitor packages to meet all the various OE specs.
DukeComment
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Re: When did the DEX-COOLRrequirement Begin
our 04 impala started to show brown sludge in the overflow bottle at about 40,000 miles. seems that if any air get into the system the sludge starts and the 04 started because the water pump seal had a very small leak that did no show up externally till later.Comment
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Re: When did the DEX-COOLRrequirement Begin
I first saw DEX-COOL in a 96 Olds that I was working on. My 95 C-1500 says nothing about it. It only says to use a coolant that meets "GM Specifications 6038-M".Comment
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Re: When did the DEX-COOLRrequirement Begin
clem-----
I had some sludge in the coolant recovery reservoir, too. However, I could not find much anywhere else. There was absolutely zero in the drained liquid. The "sludge" looked mysteriously similar to the coolant supplement that GM specifies, so I wonder if it's more related to that than to the Dex-Cool. The 04 Pontiac Grand Prix service manual does not instruct that the supplement is to be added (which surprised me since most earlier GM manuals insist that it be added) but it's possible they did install it at the factory. While I generally use the supplement, I'm not going to add it to the Grand Prix.In Appreciation of John HinckleyComment
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Re: When did the DEX-COOLRrequirement Begin
Yes, the supplement is supposed to help minimize or eliminate small leaks. Most earlier GM service manuals practically insist that it be used. In general, I have used it. I think it's made from ginger root.
The "solder leeching" issue is one that concerns me and has for quite some time. While most of the cooling system on C4 Corvettes is aluminum, the exception is the heater core. All 1984-96 Corvettes use a copper-brass heater core with soldered joints. I wish they had used aluminum with plastic tanks, but they didn't. No one should even want to THINK about replacing a heater core in a C4, especially a 1989-96. The prospect of it absolutely TERRORIZES me!In Appreciation of John HinckleyComment
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Re: When did the DEX-COOLRrequirement Begin
Jim------
Yes, most GM service manuals practically insist that the supplement be added and I generally have used it.
Removing the knock sensors is a must on a C4 when the coolant is changed. The only way around it is to use a "Flush-And-Fill" kit but I prefer not to go that route on a Corvette. If the knock sensors are not removed and the block drained, 2/3 of the coolant remains in the system after draining the radiator. Fortunately, the knock sensors are rather easy to remove so it's no big deal.In Appreciation of John HinckleyComment
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Re: When did the DEX-COOLRrequirement Begin
never saw it in the expansion bottle till dex cool came in the cars. i am sure GM used the pellets for years and i used it race engines and never saw the sludge in the aluminum tank used on corvettes and i used on race cars. i also used the pellets in my off road dirt bikes and quads and never saw any brown sludgeComment
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Re: When did the DEX-COOLRrequirement Begin
clem------
Yes, I've never seen it on "green" coolant-equipped cars, either. But it may be that the combination of Dex-Cool and the pellets causes the problem. Maybe these pellets are not so compatible with Dex-Cool. I did note that my 2004 Grand Prix service and owner's manuals make no mention of using the supplement (even though the factory may have added the pellets).In Appreciation of John HinckleyComment
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Re: When did the DEX-COOLRrequirement Begin
Folks, I believe that I was told that that Dex-Cool was introduced into the 1995 model. This booklet indicates for later 1995 models I do not know the cut off. I have an early 1995 (August-1994) and I do not have the attached Dex-Cool instructions booklet. I have since obtained one for my records.PAT, Central New Jersey and Florida Chapters
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Re: When did the DEX-COOLRrequirement Begin
All------
I've done somewhat of an "about-face" here. I've done some further research on coolants and even though the Dex-Cool has worked very well in my 1992, I'm going to switch to the Zerex G-05. While I think the Dex-Cool would continue to work well, I think the Dex-Cool is probably just a very little bit harder on the solder joints in the heater core than the G-05. Most likely it would never cause a problem but, for me, preservation of the heater core in a C4 is of HUGE importance. So, even if the difference in the coolants is only very slight in regard to solder preservation, I think it's worth making the change. In addition, the G-05 meets both GM specs 1825M, required for my 1992, and 1899M, required for most C1-C3 Corvettes. So, it's a fully approved coolant for both of my Corvettes.
I would say that as Duke has suggested in the past, the G-05 is probably the best coolant to use for any Corvette that has any copper or brass in the cooling system. Virtually all 1953-96 Corvettes fall into this category. However, 1996 owner should probably, for better or for worse, stick with GM's Dex-Cool requirement.
Dex-Cool is probably the best one to use for cars with complete aluminum cooling systems and traditional green or G-05 the best for cars with any copper-brass in the cooling system, even if the system is mostly aluminum otherwise.In Appreciation of John HinckleyComment
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Re: When did the DEX-COOLRrequirement Begin
G-05 is a good choice if one is not sure that the cooling system doesn't contain any soldered components.
It's also okay for those who just don't like Dexcool and want to use some other modern blend.
The question naturally arises: What was the last year that Corvette used any soldered components like a brass radiator and/or brass heater core?
DukeComment
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