C2: Coolant leakage - Dexcool vs. the green stuff

[Russ T.]

In the Jan '07 issue of "Corvette Fever" a writer informs tech adviser Jeff Berhardt that Quick Lube places and a GM dealer state that cars using Dex-Cool are much more prone to coolant leaks and that you don't want to convert because the orange coolant frequently turns to a "jell-like" consistency. Bernhardt agrees with him, stating that they put Dex-Cool in a '60 Corvette 283 and it "leaked in places where there were no places". Converting back to the old "green stuff" eliminated the leak while still holding 15# of pressure.

This isn't encouraging to hear, since I converted my '64 convertible to Dex-Cool six months ago. However, I have had no leaks from my new Dewitt's radiator.
I thought I'd try to get some feedback from this forum before I convert my '68 Corvette and my 2 Chevy-II's. Any opinions or experiences?

[Duke W.]

Re: C2: Coolant leakage - Dexcool vs. the green st

The "green stuff" which is inorganic antifreeze technology (IAT) is obsolete, and will eventually be hard to find. No OEMs currently use it. It provides good corrosion protection, but the inorganic salts leave deposits over time, which clog up tubes.

The industry consensus is that hybrid organic acid technology (HOAT) is the best replacement for vehicles that originally had IAT. A HOAT example is Zerex G-05. Mercedes Benz cars have been using this formulation for over 20 years, and it is now OE on all DC and Ford cars.

Dexcool, which is an organic acid technology (OAT) antifreeze provides excellent corrosion protection, but there is concern that it does not provide sufficient corrosion protection for solder joints, so it is not the best choice for vehicles that have conventional soldered brass radiators or heater cores. The Japanese OEMs also use OAT, but a different formulation than Dexcool.

I have used Dexcool in my vintage cars for ten years and have had no serious problems, but I did notice that is has more tendency to seep from joints like hose connections. Being as how it has no salts, there are no precipitates to plug tiny leaks. Conventional "green stuff" leaves a trail of white residue, which is phosphates and silicates. Dexcool only leaves the dye stain.

At the last change I switched my vintage cars to G-05, and have advised this for at least two years, reversing my previous Dexcool recommendation. I don't think you need to remove the Dexcool now, but use G-05 for the next change in two years.

All the above antifreeze products are ethylene glycol based. The different technologies refer to the corrosion inhibitor chemistry. There is as much misinformation and myth about antifreeze floating around the Web and word of mouth as there is on engine oil. You might also want to search the archives for previous discussions. There have been many.

Duke

[Mark L.]

Re: C2: Coolant leakage - Dexcool vs. the green st

Russ, I just read the same article. Coincidently I also just drained the Dex-Cool from my 66 to facilitate an intake repair. The coolant had been in the car about 8 years. I did find a little jell like material on the intake and I do recall early on I had a small coolant leak. So I guess Jeff's statements have some validity. Also there is an article in this month's Hemmings about the IAT (green), OAT (DexCool) and HOAT which is light yellow in color. This article suggests that OAT chemistry will interact with lead solder used in copper radiators. I did not see that problem with my 66 which uses a copper radiator. The article did not mention issues with HOAT.
I just restored a 67 and installed the HOAT antifreeze as it came recommended by some on this tech board. I had some leak issues at the thermostat housing and radiator hose/water pump junction but these may be related to pitted surfaces. I'd be interested in hearing any other comments. Thanks

[G B.]

Dexcool is ABSOLUTE CRAP

I just removed it from all my '96 - '05 vehicles this summer. It leaves a thick sediment that can plug up a new radiator (within 2 years in my Pontiac). I installed the new yellow stuff and will change it every year in the future.

I've always used green anti-freeze in old Corvettes.

If I wasn't clear in this post, please allow me to re-phrase my message:

DEXCOOL IS ABSOLUTE CRAP. I WOULDN'T PUT IT IN A WEEDEATER.

[Chuck S.]

Re: C2: Coolant leakage - Dexcool vs. the green st

I put Dex-cool in a late model Avalon, and had constant problems with the car overheating where there had never been any problem previously. Not being accustomed to constantly checking my coolant level, I finally figured out that the overheating was from coolant loss, but I could never find any evidence of leaks.

When I had the car warranty inspected for the dreaded "oil jelling" problem, I had the technicians change it back to Toyota coolant. They didn't find any oil jelling problem, but they did find the coolant leaks...the drain cocks on the engine were leaking like a sieve. I suppose the hot coolant must have been flashing to the atmosphere or something...I never saw any drips or pools.

Cooling systems that breathe like the old cars, i.e. draw in atmosphereic air when cooling, could have problems with Dexcool gelling and clogging the radiator. Late model cooling systems that don't breathe as much (semi-sealed with an overflow reservoir), but are not designed to use Dexcool (materials, leak tightness) will have problems with leaks.

I have Dexcool in my C6, and GM guarantees the car for three years...if the cooling system doesn't leak, the car doesn't overheat, and there is no OTHER evidence of problems, I'll leave it in there. When it's service life expires, I may even consider it again if I haven't seen any evidence of problems; if it causes any problems, I'll look at Zerex or, uh...Toyota coolant.

[Chuck S.]

For An Old Car, Forget Dexcool, Use the Zerex *NM*

[Dick W.]

Re: C2: Coolant leakage - Dexcool vs. the green st

Most automotive sources recommend that "if it came with green, replace with green. The systems were designed with the IAT technology in mind. They recommend the use of Dexcool ONLY in vehicles that originally came with it.

[Patrick T.]

Why does Tom DeWitt insist on Dexcool....

when installing one of his reproduction radiators in a car? Inquiring minds want to know. PT

[Kurt B.]

Re: Why does Tom DeWitt insist on Dexcool....

I have Tom Dewitts factory correct radiator in my 68 but I use the Zerex antifreeze. I had no problems all summer long and don't expect any this winter since I don't drive it in the winter.
Garage is warm, no problem.
Kurt

[Ralph S.]

Re: Dexcool is ABSOLUTE CRAP

My 2003 Silverado V-6 had an intake manifold gasket leak and the Dexcool clogged up the oil filter, I cut the filter open and it was like Jello inside

[Mike B.]

Re: C2: Coolant leakage - Dexcool vs. the green st

For those that need to know more here are two great links. One has info about every fluid used under the hood, the other is specific to Zerex products.

http://theoildrop.server101.com/forums/ubbthreads.php?Cat=0

https://www.valvoline-technology.com/data/VALV/ValvExtSecurity.nsf/fsZerex?OpenFrameSet