C7 coolant
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Racer
Joined: Feb 2015
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From: Southwestern FL
C7 coolant
Ok, Im approaching 5 years and my car is a weekend driver with only 10,000 miles on it. Should I have the coolant replaced with my next oil change? What have others done here?
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Oct 18, 2019, 09:50 PM
Tech Contributor
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From: Charlotte, NC (formerly Endicott, NY)
Gm says to change the Dex at 5 years or 150K miles. Change it at 5 years as it doesn't change color like the old green coolants that got all rusty did. It isn't hard to do if you do it yourself other than getting rid of the old coolant. Remember the coolant had a 40/60 ratio of Dex/Water when shipped from the factory so you can't purchase 50/50 mix. C7 Coolant capacity is 11.3 quarts. There are two ways to get the proper mix on the change over. One way is by mixing 4 quarts of Dex with 6 quarts of water. Then just pull the drain plug on the radiator and let the coolant drain into a large pan. Once empty refill with your new mix and be done with it. If you want to get all of the old coolant out of the engine and heater core then it takes more effort. First, drain the coolant then refill with clean drinking water and run the engine until the thermostat opens. After a minute of operating with the thermostat open shut off engine and drain the coolant again. Repeat until the drained coolant is clear. Then add 4.5 quarts of DexCool and top off with clean drinking water. The biggest problem is getting rid of the old coolant as it is poisonous. It causes liver damage and Animals and Kids like to drink the stuff because it tastes sweet.
Bill
Bill
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Gm says to change the Dex at 5 years or 150K miles. Change it at 5 years as it doesn't change color like the old green coolants that got all rusty did. It isn't hard to do if you do it yourself other than getting rid of the old coolant. Remember the coolant had a 40/60 ratio of Dex/Water when shipped from the factory so you can't purchase 50/50 mix. C7 Coolant capacity is 11.3 quarts. There are two ways to get the proper mix on the change over. One way is by mixing 4 quarts of Dex with 6 quarts of water. Then just pull the drain plug on the radiator and let the coolant drain into a large pan. Once empty refill with your new mix and be done with it. If you want to get all of the old coolant out of the engine and heater core then it takes more effort. First, drain the coolant then refill with clean drinking water and run the engine until the thermostat opens. After a minute of operating with the thermostat open shut off engine and drain the coolant again. Repeat until the drained coolant is clear. Then add 4.5 quarts of DexCool and top off with clean drinking water. The biggest problem is getting rid of the old coolant as it is poisonous. It causes liver damage and Animals and Kids like to drink the stuff because it tastes sweet.
Bill
Bill
Melting Slicks
Joined: Aug 2016
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From: MOUNTAIN HOME Arkansas
Bill's DIY drain, refill with water, etc. works well. I just did this on my '07 F150 & ended up with exactly the correct amount in radiator/reservoir.
Last edited by madrob2020; Oct 20, 2019 at 08:27 PM.
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Bill
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From: Milwaukee WI
Gm says to change the Dex at 5 years or 150K miles. Change it at 5 years as it doesn't change color like the old green coolants that got all rusty did. It isn't hard to do if you do it yourself other than getting rid of the old coolant. Remember the coolant had a 40/60 ratio of Dex/Water when shipped from the factory so you can't purchase 50/50 mix. C7 Coolant capacity is 11.3 quarts. There are two ways to get the proper mix on the change over. One way is by mixing 4 quarts of Dex with 6 quarts of water. Then just pull the drain plug on the radiator and let the coolant drain into a large pan. Once empty refill with your new mix and be done with it. If you want to get all of the old coolant out of the engine and heater core then it takes more effort. First, drain the coolant then refill with clean drinking water and run the engine until the thermostat opens. After a minute of operating with the thermostat open shut off engine and drain the coolant again. Repeat until the drained coolant is clear. Then add 4.5 quarts of DexCool and top off with clean drinking water. The biggest problem is getting rid of the old coolant as it is poisonous. It causes liver damage and Animals and Kids like to drink the stuff because it tastes sweet.
Bill
Bill
In addition, I encountered what I thought was a concern after completing several drain cycles until the coolant was clear. At that time, the entire cooling system is pure water, either drinking water or distilled. I added 4.5 quarts of DexCool after the last drain expecting to achieve the 40% coolant mix. The recovery tank had to be topped off with clear water after the coolant was in the system. Following a warming cycle with the engine running, I checked the freeze point of the coolant mix in the recovery tank and found it to be around zero degrees. I was concerned the proper percentage of coolant had not been achieved.
I discovered the protection temperature decreased each time I ran the car and let it cool after completing the change procedure. Today, I checked the protection level again after about 15 warm/cool cycles and the protection is now at the expected level of nearly -30 degrees.
Coolant is not cycled through the coolant recovery tank continuously during a drive cycle. As the coolant temperature rises, coolant is pushed to the recovery tank and drawn back to the radiator as it cools. Several cycles are needed to approach a complete mixture of coolant and water as evidenced by a coolant testing tool.
If coolant is changed shortly before putting the car in storage, the freeze protection of the coolant in the recovery tank may not be far below zero. It is a good idea to drive the car through several warm/cool cycles after the change before placing in storage for the winter.
Last edited by vettetwo; Nov 5, 2019 at 03:00 PM.
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Second, contaminants gather in the coolant over time which may damage the cooling system components
Just changed the coolant in my 5-year-old 15000 mile Z06, the old coolant was opaque and sort of cloudy looking while the new fluid was orange and translucent. There was a lot of stuff in the fluid that wasn't there when the car was first built. If your 20 year old car is still running on 20 year old coolant I suspect it is closer to mud now than it was when it was new. Sure you have the same freeze and boilover protection but Antifreeze also has water pump lubricant and corrosion restricting chemicals that lose their potency over time. With the green antifreeze, this happens in two years. With Dex-Cool this happens over a period of 5 years/150K miles whichever comes first.
Bill
Drifting
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From: Hill Country Texas
Clean drinking water is a good way to put it. De-mineralized and most importantly de-ionized water is the way to go. Distilled water is actually ionically imbalanced and that isn't all that great to expose to all of the Al in your Al radiator, heat exchanger, Al block, and Al cylinder heads. Actually, softened water via the common residential sodium-ion exchange process is a great place to get your water.
https://www.hyperlube.com/blog/blog/...ooling-system/
Many people have “heard” that distilled water is the best water to use in a cooling system. This is wrong! While it is certainly true that distilled water’s purity prevents electrolysis and scale/deposit formation, it unfortunately comes with a potentially very damaging side effect.
During the distillation process, water is vaporized into its gaseous phase, so all its impurities are left behind. These impurities include a number of minerals, including “calcium” and “magnesium,” the two components of water “hardness.” The water is then condensed back into its liquid phase, so the resulting liquid is pure water – in fact, some of the purest water on earth. But the problem is that when water is distilled, or “stripped,” of its minerals and impurities, the resulting solution is composed of chemically imbalanced “ions.” This leaves distilled water “ionically hungry,” so it will actually strip electrons from the metals in a cooling system as it attempts to chemically re-balance itself. As it chemically removes electrons from the metals of cooling system components, distilled water eventually does extreme damage that could lead to cooling system failure.
So what’s the answer? Softened water. During the water softening process, the same impurities and minerals are removed from water as during the distillation process – but with one very important distinction. Rather than STRIPPING the impurities from water, softening EXCHANGES the impurities with a sodium ion. The resulting solution is chemically and ionically balanced, making softened water very stable, very pure, and non-threatening to cooling system metals.
There seems to be a perceptual issue with regard to the usage of softened water in cooling systems by auto enthusiasts. Many mistakenly believe that because salt is added to water softeners, then softened water must contain salt, a substance of course known to be very corrosive. Nothing could be further from the truth. The salt you add to a water softener is NaCl, or sodium chloride.
During the softening process, only the sodium ion is exchanged into the water. Therefore, softened water does NOT contain corrosive salt.
What are the benefits of using softened water? Soft water lacks most of the impurities of tap water, meaning it far less conductive (i.e. less damage from electrolysis) and will not form deposits (i.e. less possibility of overheating). However, if you use Hy-per Lube Super Coolant, you don’t need to use softened water. Hy-per Lube Super Coolant contains molybdate, a form of the semi-precious metal “molybdenum,” which is proven to be extremely effective in preventing galvanic action and electrolysis – regardless of what type of water is used. Hy-Per Lube Super Coolant also contains polymer dispersants which keep water hardness in solution, thus preventing the formation of insulative scales and deposits. So regardless of whether you use softened water or tap water, you need not worry about these issues when you use Hy-Per Lube Super Coolant. This is actually one of the important benefits of the product, because not everybody has easy access to softened water.
But please – PLEASE! – do not use distilled water in your automotive cooling system.
https://www.hyperlube.com/blog/blog/...ooling-system/
WHY YOU SHOULD NEVER USE DISTILLED WATER IN YOUR COOLING SYSTEM
- Posted on: Apr 26 2018
- By: Hy-per Web Crew
Many people have “heard” that distilled water is the best water to use in a cooling system. This is wrong! While it is certainly true that distilled water’s purity prevents electrolysis and scale/deposit formation, it unfortunately comes with a potentially very damaging side effect.
During the distillation process, water is vaporized into its gaseous phase, so all its impurities are left behind. These impurities include a number of minerals, including “calcium” and “magnesium,” the two components of water “hardness.” The water is then condensed back into its liquid phase, so the resulting liquid is pure water – in fact, some of the purest water on earth. But the problem is that when water is distilled, or “stripped,” of its minerals and impurities, the resulting solution is composed of chemically imbalanced “ions.” This leaves distilled water “ionically hungry,” so it will actually strip electrons from the metals in a cooling system as it attempts to chemically re-balance itself. As it chemically removes electrons from the metals of cooling system components, distilled water eventually does extreme damage that could lead to cooling system failure.
So what’s the answer? Softened water. During the water softening process, the same impurities and minerals are removed from water as during the distillation process – but with one very important distinction. Rather than STRIPPING the impurities from water, softening EXCHANGES the impurities with a sodium ion. The resulting solution is chemically and ionically balanced, making softened water very stable, very pure, and non-threatening to cooling system metals.
There seems to be a perceptual issue with regard to the usage of softened water in cooling systems by auto enthusiasts. Many mistakenly believe that because salt is added to water softeners, then softened water must contain salt, a substance of course known to be very corrosive. Nothing could be further from the truth. The salt you add to a water softener is NaCl, or sodium chloride.
During the softening process, only the sodium ion is exchanged into the water. Therefore, softened water does NOT contain corrosive salt.
What are the benefits of using softened water? Soft water lacks most of the impurities of tap water, meaning it far less conductive (i.e. less damage from electrolysis) and will not form deposits (i.e. less possibility of overheating). However, if you use Hy-per Lube Super Coolant, you don’t need to use softened water. Hy-per Lube Super Coolant contains molybdate, a form of the semi-precious metal “molybdenum,” which is proven to be extremely effective in preventing galvanic action and electrolysis – regardless of what type of water is used. Hy-Per Lube Super Coolant also contains polymer dispersants which keep water hardness in solution, thus preventing the formation of insulative scales and deposits. So regardless of whether you use softened water or tap water, you need not worry about these issues when you use Hy-Per Lube Super Coolant. This is actually one of the important benefits of the product, because not everybody has easy access to softened water.
But please – PLEASE! – do not use distilled water in your automotive cooling system.
Last edited by BigVette427; Mar 2, 2021 at 04:09 PM.
Pro
Joined: Nov 2013
Posts: 693
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From: Milwaukee WI
Clean drinking water is a good way to put it. De-mineralized and most importantly de-ionized water is the way to go. Distilled water is actually ionically imbalanced and that isn't all that great to expose to all of the Al in your Al radiator, heat exchanger, Al block, and Al cylinder heads. Actually, softened water via the common residential sodium-ion exchange process is a great place to get your water.
https://www.hyperlube.com/blog/blog/...ooling-system/
https://www.hyperlube.com/blog/blog/...ooling-system/
Distilled water should not be used by itself in an automobile cooling system and that is why it is important to mix that distilled water with the proper amount of anti-freeze such as Prestone, Peak, ACDelco Dex-Cool, etc.
The Prestone website drain and fill instructions explicitly state to use distilled water with their Prestone Concentrate.
The Peak website has instruction video's which also state to use distilled water with their anti-freeze concentrate. They also state the pre-mixed Peak anti-freeze contains their concentrate mixed with distilled water.
I believe the statement from Hyperlube is accurate in that it does not use the term anti-freeze and simply states distilled water should not be used without explaining completely that they mean distilled water should not be used by itself.
Tech Contributor
Joined: Oct 1999
Posts: 41,030
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From: Charlotte, NC (formerly Endicott, NY)
This is an interesting article and can be misconstrued in conflict with the drain and fill instructions on anti-freeze product websites.
Distilled water should not be used by itself in an automobile cooling system and that is why it is important to mix that distilled water with the proper amount of anti-freeze such as Prestone, Peak, ACDelco Dex-Cool, etc.
The Prestone website drain and fill instructions explicitly state to use distilled water with their Prestone Concentrate.
The Peak website has instruction video's which also state to use distilled water with their anti-freeze concentrate. They also state the pre-mixed Peak anti-freeze contains their concentrate mixed with distilled water.
I believe the statement from Hyperlube is accurate in that it does not use the term anti-freeze and simply states distilled water should not be used without explaining completely that they mean distilled water should not be used by itself.
Distilled water should not be used by itself in an automobile cooling system and that is why it is important to mix that distilled water with the proper amount of anti-freeze such as Prestone, Peak, ACDelco Dex-Cool, etc.
The Prestone website drain and fill instructions explicitly state to use distilled water with their Prestone Concentrate.
The Peak website has instruction video's which also state to use distilled water with their anti-freeze concentrate. They also state the pre-mixed Peak anti-freeze contains their concentrate mixed with distilled water.
I believe the statement from Hyperlube is accurate in that it does not use the term anti-freeze and simply states distilled water should not be used without explaining completely that they mean distilled water should not be used by itself.
Bill
Cruising
Joined: Aug 2022
Posts: 10
Likes: 2
From: Fort Collins, CO
1.65 Gallons came out
Bill Thanks for all your recommendations and you are the top source of info for me on this forum. I just changed coolant the quick way and only had 1.65 gallons come out, so less than 7 quarts. I used the recommended 40 Dexcool and 60 drinking water, and will change it again in a few months, to ensure I am good for another 5 years.
Pro
Joined: Nov 2013
Posts: 693
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From: Milwaukee WI
Bill Thanks for all your recommendations and you are the top source of info for me on this forum. I just changed coolant the quick way and only had 1.65 gallons come out, so less than 7 quarts. I used the recommended 40 Dexcool and 60 drinking water, and will change it again in a few months, to ensure I am good for another 5 years.
If you drive for a few months, you may have completely mixed the new and old mixture assuming completion of 15-20 drive cycles. I have found it takes that many drive cycles where the coolant is pushed into and out of the reservoir tank sufficient to mix nearly completely. Keep in mind, the coolant in the reservoir tank does not circulate through the system so there must be drive cycles to cause the new and old to mix.
At the time you drain once again and remove another 1.65 gallons (6.6qt) of that coolant containing 6.6qt "new" coolant mix and 4.7qt old coolant that was left from the original fill. By adding new coolant, you are adding 2.64qt of new DexCool to the now contaminated mixture which contains comingled coolant that is 58% two month old DexCool and 42% old DexCool.
Your resulting mixture will not protect your cooling system for 5 years because of the depleted lubricating and residual contaminants. There are two ways you can achieve another 5 year protection of the cooling system. One way is a flush and fill where the entire contents are removed and replaced with a fresh 40% fill. The second is to do several drain/fill until you achieve clear water on the last drain/fill. After either method, you cannot use the premixed coolant because there will be residual clear water estimated to be approximately 4.7 quarts. The refill should be 2.64 quarts undiluted DexCool which will mix with the clear water after several drive cycles. As I mentioned earlier, I determined the complete mix of water and DexCool was not achieved until 17 drive cycles as determined by measuring the protection of the coolant in the reservoir tank which started at 0* right after the last fill and -30* after 17 drive cycles.
I am confident my C7 cooling system is protected for a full 5 years. Yours is not.
Cruising
Joined: Aug 2022
Posts: 10
Likes: 2
From: Fort Collins, CO
Thank you Vettetwo for the comprehensive reality check! I live in CO and my 2018 Z06 will never be exposed to temps under 35 degrees. I cut corners where I can to save time and cost, but everything you stated is logical and sound, so my Risk/Reward ratio just increased, so I will do the water method as that is the simpleton way.
My only question: you mentioned "After either method, you cannot use the premixed coolant because there will be residual clear water estimated to be approximately 4.7 quarts. The refill should be 2.64 quarts undiluted DexCool which will mix with the clear water after several drive cycles."
With the system being 11.3 quarts, and after only clear water is draining out which means there is appx 4.7 quarts of only water in the system, for the Dexcool i was thinking that 11.3 quarts x .40 = 4.52 quarts of Dexcool and 6.78 quarts water for the proper mix. So after only water has drained out, shouldn't I fill with 4.52 qts Dexcool and an additional 2.08 qts water to make the optimal 40% dexcool mix.
Thank you for your time educating me and most certainly some others who like to cut corners where they see no risk.
My only question: you mentioned "After either method, you cannot use the premixed coolant because there will be residual clear water estimated to be approximately 4.7 quarts. The refill should be 2.64 quarts undiluted DexCool which will mix with the clear water after several drive cycles."
With the system being 11.3 quarts, and after only clear water is draining out which means there is appx 4.7 quarts of only water in the system, for the Dexcool i was thinking that 11.3 quarts x .40 = 4.52 quarts of Dexcool and 6.78 quarts water for the proper mix. So after only water has drained out, shouldn't I fill with 4.52 qts Dexcool and an additional 2.08 qts water to make the optimal 40% dexcool mix.
Thank you for your time educating me and most certainly some others who like to cut corners where they see no risk.
Pro
Joined: Nov 2013
Posts: 693
Likes: 158
From: Milwaukee WI
Thank you Vettetwo for the comprehensive reality check! I live in CO and my 2018 Z06 will never be exposed to temps under 35 degrees. I cut corners where I can to save time and cost, but everything you stated is logical and sound, so my Risk/Reward ratio just increased, so I will do the water method as that is the simpleton way.
My only question: you mentioned "After either method, you cannot use the premixed coolant because there will be residual clear water estimated to be approximately 4.7 quarts. The refill should be 2.64 quarts undiluted DexCool which will mix with the clear water after several drive cycles."
With the system being 11.3 quarts, and after only clear water is draining out which means there is appx 4.7 quarts of only water in the system, for the Dexcool i was thinking that 11.3 quarts x .40 = 4.52 quarts of Dexcool and 6.78 quarts water for the proper mix. So after only water has drained out, shouldn't I fill with 4.52 qts Dexcool and an additional 2.08 qts water to make the optimal 40% dexcool mix.
Thank you for your time educating me and most certainly some others who like to cut corners where they see no risk.
My only question: you mentioned "After either method, you cannot use the premixed coolant because there will be residual clear water estimated to be approximately 4.7 quarts. The refill should be 2.64 quarts undiluted DexCool which will mix with the clear water after several drive cycles."
With the system being 11.3 quarts, and after only clear water is draining out which means there is appx 4.7 quarts of only water in the system, for the Dexcool i was thinking that 11.3 quarts x .40 = 4.52 quarts of Dexcool and 6.78 quarts water for the proper mix. So after only water has drained out, shouldn't I fill with 4.52 qts Dexcool and an additional 2.08 qts water to make the optimal 40% dexcool mix.
Thank you for your time educating me and most certainly some others who like to cut corners where they see no risk.
Glad to hear you are taking good care of your C7.
Team Owner
Joined: Jul 2004
Posts: 28,372
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From: Hartford WI
Thank you Vettetwo for the comprehensive reality check! I live in CO and my 2018 Z06 will never be exposed to temps under 35 degrees. I cut corners where I can to save time and cost, but everything you stated is logical and sound, so my Risk/Reward ratio just increased, so I will do the water method as that is the simpleton way.