squeaker66

I plan on flushing the cooling system this weekend in my 66 300hp Roadster and would like to know what type of coolant/anti-freeze use.

Is there any advantage or harm in running the newer ACDelco Dex-Cool vs. say the standard silicone containing prestone, etc.

Kent

stepinwolf

I have contacted the manufacturer concerning it's use in our older vehicles, and was told that it ( Dex-Cool ) had been developed for the later models that were built mostly with aluminium components.

I had originally used this in my restoration/rebuild, but have since swapped it out with the regular anti-freeze.

Your choice



Drive your Corvettes as if each day was your last

Donald #31176

Kent,
I currently am using the DexCool antifreeze in my 62.Its been in there for about a year and a half with no side effects. However this fall Im going to change to the HOAT type of antifreeze G05 made by Zerex. This is the recommended type to use by our teches in our car club.

Scott Marzahl

Yes, there has been lots of discussion and recommendations regarding switching to the G05 antifreeze, I just picked up two gallons myself.

vark_wso

Does anyone know if there is one type that is more suitable for aluminum manifolds/radiators vs. cast iron/copper?

1965L76

What are the recommendations for the percentage of coolant versus distilled water? How often should the coolant be changed?

SWCDuke

The current industry consensus is cars that were OEM filled with traditional green antifreeze (which is being phased out because it is no longer used by OEMs) should switch to a hybrid organic acid technology (HOAT) antifreeze, and Zerex G-05 is an appropriate selection that is commonly available from auto parts outlets.

The recommended change interval is in owner's manuals, and for cars or our vintage it is typically two years or 24 to 30K miles, whichever comes first. In the case of most of our cars that don't see high annual mileage accumulation, it comes down to changing it on a time schedule.

A fifty percent concentration of antifreeze with water is the generally recommended concentration for maximum freezing and corrosion protection, but the antifreeze concentration should not exceed 70 percent. I also recommend distilled water as the mixing agent in order to avoid the introduction of "foreign" chemicals that are in some potable water that may not be compatible with the chemicals that makeup the corrosion inhibitor package.

Duke

Stick

[QUOTE=SWCDuke]The current industry consensus is cars that were OEM filled with traditional green antifreeze (which is being phased out because it is no longer used by OEMs) should switch to a hybrid organic acid technology (HOAT) antifreeze, and Zerex G-05 is an appropriate selection that is commonly available from auto parts outlets.

I remember there was a caution to make absolutely sure that all the Dex-Cool was out of your system before switching back to green. Is the HOAT more compatible with green?

joec

Not to hijack the thread here but.. So know since I have my radiator out (new Dewitts going in) how do I fully flush the system, which I imagine you gotta do to go over to HOAT.. JohnZ told me about the 2 spots on the block to drain the water jackets, but now how do I get it out of the heater core??

Thanks,

/joe

SWCDuke

Dexcool has a pure organic corrosion inhibitor package and inorganics can reduce it's effectiveness, so the recommendation to thoroughly flush the system to remove all traces of "green" when switching to Dexcool is well advised.

Don't know about the reverse, or why anyone would want to go that way, but caution would dictate a thorough system flush if going "backward" from Dexcool to green. The "flush" here is just a thorough flush with fresh water - no "chemical flushes" needed.

HOATs contain organic corrosion inhibitors with a small dose of inorganics, so it is more compatible with green, but when you switch to a HOAT from any other type, I would still advise a thorough fresh water flush to remove all the green.

If you are replacing with a like type, just drain and fill, but a fresh water flush is never a bad idea IMO.

Duke

SWCDuke

Disconnect the heater inlet hose at the inlet manifold and flush both ways - through the heater circuit and through the engine. This will give the entire cooling system the thorough douche it needs, especially if the radiator is not installed

Duke

Veet 66

I read an article that said do not use distilled water.

JohnZ

Some chemists may disagree, but every new car owner's manual makes it VERY clear that any time the coolant mix is replaced or the system is topped-off, only distilled or de-ionized water should be used, "or engine or cooling system damage may occur which may not be covered by your new vehicle warranty".

SWCDuke

A long time ago there was a theory that pure distilled water would make a good coolant, and that was a BIG MISTAKE. You have to understand the context of the "no distilled water" warning. It means don't use straight distilled water with no antifreeze or other corrosion inhibitors.

Antifreezes are blended with a carefully contolled mix of various chemicals that prevent corrosion. If you add water that has other dissolved chemicals, and all domestic water does, then you are changing the blend, and you don't know if there are incompatibillites. Isn't his just intuitive?

Distilled water has no dissolved chemicals so when you MIX IT WITH ANTIFREEZE you don't upset the chemical balance.

All domestic water has dissolved minerals, particularly calcium. Also, most domestic water has a small amount of chorline added to control bacteria, and chlorine, in particular, will accelerate cooling system corrosion.

Best corrosion protection is to use distilled water with antifreeze, the latter being at least 50 percent concentration, but no more than 70 percent.

Duke

norvalwilhelm

I bought a new aluminum rad and ran Preston/ the green stuff. After one year I drained the cooling system and found the inside of my new rad was crudded up with white deposits. I changed to dexcool, orange in color and the next fall after draining the cooling system found the rad looked like new inside.
I am a believer in dex cool.

Mecom Racer

Everything I've heard about Dexcool warns that it must only be used in a completely sealed system or it will sludge up in short time.

Solid327

Assuming a freshly restored vintage engine, all cast iron except the intake, flushed and cleaned brass heater core and a new aluminum Dewitt radiator, I wonder what Tom would recommend? Dexcool or the green stuff??

SWCDuke

That's not true! These antifreeze discussions are as boarish as motor oil discussions with all the myths and misinformation floating around.

Dexcool DOES appear to have a higher propenisty to sludge and/or cause corrosion if the coolant level is run at much lower than the OE minimum quantity for EXTENDED mileage, but that won't happen if the owner regularly checks the coolant level which is HIS/HER responsibility. This is easy on a modern car, since all that is required is a visual inspection of the translucent recovery tank. On a vintage Corvette you actually have to remove the pressure cap to check level.

I've used Dexcool in ALL my cars since 1995, which was before it was even generally available at auto parts store, but there is one nagging issue with older cars. Dexcool may not (the evidence is not absolutely conclusive) provide adquate protection for old high lead solders used in vintage heater cores and radiators. And even if your Corvette has an aluminum radiator, it still has a brass heater core. This issue is "lead leaching" and this may reduce solder joint strength.

For this reason I have backed away from my previous Dexcool recommendation and now recommend Zerex G-05 for vintage Corvettes, however, I will add that after ten years Dexcool has NOT created any cooling system problems for me, and all my brass radiators and heater cores are leak free, but I'm switching at the next coolant change.

Duke

Veet 66

I sent an email to DeWitt to see what he thinks since he is the radiator expert.I went to Pep Boys and the G05 antifreeze says ford and other cars but did not say GM. Was I looking at the wrong stuff?

Mecom Racer

Probably not. GM pays Dexcool so they're not going to spend money getting their name on the G-05 too.