Cooling Questions

[Robert G.]

I have recently purchased a '66 convertible, I'm kind of a novice and have a few questions. The car has it's original radiator and overflow tank and I know I must use the correct type of anti-freeze that can be used with aluminum components, what is the best anti-freeze to use? Also I am located in SW Colorado and assume a 180 degree thermostat is the proper one to use.
One last question (for now that is) when draining the radiator and block does that drain the heater core? If not how does one drain that part of the system.
Thanks for your help,
Rob Goodrich
#65905

[Michael J.]

Re: Questions

Not sure if you have a big or small block, but regardless, I think the conventional wisdom is still that an original cooling system in that year Corvette should use a 50-50 mix of Zerex G-05 and distilled water. That is best suited to the cooling system materials and has the proper additives to guard against corrosion and provide the best cooling. I live in northern NM, and I use a 185 thermostat in all my C2s, but 180 should be fine, just get a good one. Draining the cooling system is not an easy task, and it would be best to know if you have a big block or small block before we can provide a good answer.

[Edward D.]

Re: Questions

I use the Prestone glycol 50/50 premix (the green stuff) in my original 66 which still has its original dated radiator. Use same for customer cars. Change about every 2 years. Don't worry about heater core and block unless you need to do a complete flush, simply draining radiator and refilling is good enough. I use a 160 thermostat, but its hot here in Florida, the 180 is the correct factory thermostat.

[Richard G.]

Re: Questions

I would confirm the rubber radiator rubber isolators are in good shape and change out the fluid on a regular bases.
Draining the block and radiator should also remove the fluid in the heater core. (At least on a SBC)
Typically one can only easily access the drain on the left side. The one on the right is way more difficult to get at.
When I change the antifreeze I do one side of the block and the radiator and call it good.
Rick

[Joe L.]

Re: Questions

I have recently purchased a '66 convertible, I'm kind of a novice and have a few questions. The car has it's original radiator and overflow tank and I know I must use the correct type of anti-freeze that can be used with aluminum components, what is the best anti-freeze to use? Also I am located in SW Colorado and assume a 180 degree thermostat is the proper one to use.
One last question (for now that is) when draining the radiator and block does that drain the heater core? If not how does one drain that part of the system.
Thanks for your help,
Rob Goodrich
#65905

Rob------


The best coolant for aluminum is DexCool. However, you have other types of metals in your cooling system and DexCool is not the best for those. So, as others have mentioned Zerex G-05 is the best overall. I use a 60/40 mix.

[Michael B.]

Re: Questions

I don't wish to hijack the thread but I've got a question on the proper antifreeze to use. In the February 2019 issue of Auto Restorer a reader submitted a question concerning this issue. He had a collection of British cars and had recently received a warning from his club concerning the use of several popular brands, including Zerex G-05. The warning from his club follows:

"Under no circumstances should an Extendened Life antifreeze (which utilizes Organic Additive Technology, OAT, H-OAT, or N-OAT) as one of its chemicals ever be used in our cars over 10 years old. It attacks the gaskets and gasket cements in our cars causing major leaks. The Silver Ghost Association Rolls Royce people have documented massive cooling system failures caused by these antifreeze products. The antifreeze that can be used safely in our cars uses an older fashioned Inorganic Additive Technology. You cannot tell by the color of the antifreeze if it's safe to use. Also, the product may be labeled "Safe For older Cars" meaning 10 years old at most. Brands to be avoided are all Prestone lines and Zerex G-05 in the Gold container. Acceptable brands are Peak, Peak HD Product Sierra, and Zerex original Green." There was further speculation that these antifreeze products could eat away at the solder joints in copper radiators although that was undocumented.

Not knowing anything about British car engines I'm curious if this is isolated to their engines or if there is crossover to our cast iron blocks and gaskets. Anyone know for sure?

Thanks,

Mike

[Joe L.]

Re: Questions

I don't wish to hijack the thread but I've got a question on the proper antifreeze to use. In the February 2019 issue of Auto Restorer a reader submitted a question concerning this issue. He had a collection of British cars and had recently received a warning from his club concerning the use of several popular brands, including Zerex G-05. The warning from his club follows:

"Under no circumstances should an Extendened Life antifreeze (which utilizes Organic Additive Technology, OAT, H-OAT, or N-OAT) as one of its chemicals ever be used in our cars over 10 years old. It attacks the gaskets and gasket cements in our cars causing major leaks. The Silver Ghost Association Rolls Royce people have documented massive cooling system failures caused by these antifreeze products. The antifreeze that can be used safely in our cars uses an older fashioned Inorganic Additive Technology. You cannot tell by the color of the antifreeze if it's safe to use. Also, the product may be labeled "Safe For older Cars" meaning 10 years old at most. Brands to be avoided are all Prestone lines and Zerex G-05 in the Gold container. Acceptable brands are Peak, Peak HD Product Sierra, and Zerex original Green." There was further speculation that these antifreeze products could eat away at the solder joints in copper radiators although that was undocumented.

Not knowing anything about British car engines I'm curious if this is isolated to their engines or if there is crossover to our cast iron blocks and gaskets. Anyone know for sure?

Thanks,

Mike

Mike------


I cannot speak for the British cars. However, most of the current coolants such as traditional green Prestone and Zerex G-05 meet GM's requirements for cars going back to the 50's. For example, my 1969 Corvette (and, probably, most previous and many later Corvettes) requires coolant meeting GM spec 1899-M. Many later GM cars, prior to DexCool, require coolant meeting GM specification 1825-M. Both Prestone green and Zerex G-05 specifically meet these GM standards and I'm sure that most of the other coolants on the market do, too. The fact that they specifically meet the GM standard is about all I need to know. The GM standards are comprehensive in scope and cover a whole host of issues including corrosivity and compatibility with gasket and other materials.

As far as the solder joints in copper radiators (and heater cores) go, Zerex G-05 is the least corrosive to solder joints as any coolant I know of on the market today. That's one of the primary reasons I use and recommend it for cars that have copper radiators OR copper heater cores.

[Michael B.]

Re: Questions

Joe,

After seeing that warning in Auto Restorer I started using Zerex Original Green. It also meets 1899-M and 1825-M specs but states it's a Low Silicate, Inorganic Additive technology product for use in GM 1996 and older vehicles. Apparently an antifreeze can meet those GM specs with either the IAT or OAT technology. I can't help but wonder if these additives (whatever they are) make a difference, and if not, why would Zerex market a line specifically for older vehicles?

I think the world is getting too dang complicated. Just when I got the oil figured out (thanks to Duke's article) here comes the antifreeze.

Thanks for your thoughts.

Mike

[Joe L.]

Re: Questions

Joe,

After seeing that warning in Auto Restorer I started using Zerex Original Green. It also meets 1899-M and 1825-M specs but states it's a Low Silicate, Inorganic Additive technology product for use in GM 1996 and older vehicles. Apparently an antifreeze can meet those GM specs with either the IAT or OAT technology. I can't help but wonder if these additives (whatever they are) make a difference, and if not, why would Zerex market a line specifically for older vehicles?

I think the world is getting too dang complicated. Just when I got the oil figured out (thanks to Duke's article) here comes the antifreeze.

Thanks for your thoughts.

Mike

Mike------

In 1996 GM started specifying DexCool (GM spec 6277M) since by that time the vast majority of GM vehicles had aluminum radiators, aluminum heater cores, and aluminum heads. An exception was 1996 Corvettes which still used a copper/brass heater core. I don't recommend the use of Dexcool for 1996 Corvettes. It's one of the few cases in which I deviate from the GM specs. For 1997 Corvettes and later, use DexCool.

I don't go by the additive or technology type. I go by whether it meets the GM spec for the particular car. If it meets the appropriate spec, I say it's fine to use. GM knows more than I do (except for 1996 Corvettes).

By the way, in offering Zerex green they are not offering a coolant specifically for older vehicles. They are offering a coolant for vehicles requiring coolant with a GM spec of 1899-M and 1825-M. It likely also meets specs of other auto manufacturers, too. Zerex G-05 and Prestone green also meet GM spec 1899-M and 1825-M and, likely, other auto manufacturers. So, I really do not see any compatibility difference between Zerex green and Zerex G-05 or Prestone green.

Most, if not all, 1997 and later GM vehicles require DexCool (GM spec 6277-M). In order to meet that spec one must use a coolant that specifically states it meets it. I don't know of any coolant that meets the GM 1899-M, 1825-M and 6277-M specs but there may be some.

[Michael B.]

Re: Questions

I did a little research concerning the OAT/IAT question and discovered there are credible sources suggesting the OAT additives are corrosive to solder and are not recommended for use in copper radiator vehicles. I read it on the Internet so it has to be true; right?

Here's the link to a Hemmings article.

https://www.hemmings.com/blog/2014/08/01/tech-101-the-colors-of-antifreeze/

[Joe L.]

Re: Questions

I did a little research concerning the OAT/IAT question and discovered there are credible sources suggesting the OAT additives are corrosive to solder and are not recommended for use in copper radiator vehicles. I read it on the Internet so it has to be true; right?

Here's the link to a Hemmings article.

https://www.hemmings.com/blog/2014/0...of-antifreeze/

Michael-------


Zerex G-05 is a HOAT coolant. As I said before, it is the best for copper/brass systems with solder joints. There is no coolant I know of that's easier on solder joints or copper/brass components.

[Larry M.]

Re: Questions

Michael-------


Zerex G-05 is a HOAT coolant. As I said before, it is the best for copper/brass systems with solder joints. There is no coolant I know of that's easier on solder joints or copper/brass components.

Here are the specs and corrosion information for Zerex G-05. Mike and others can read for themselves. https://www.consulab.com/files/zerexg05TechBulletin.pdf

I have been using it for 20 years in my 1967 Corvette with no leaks, or corrosion, or cooling issues. I replace every 4-5 years. I used distilled water as needed.

Corrosion data for other Zerex coolants is available also. Prestone no longer publishes this information. I used to work for Union Carbide and had access to all this Prestone and competitors data............but no longer.

Larry