Distilled, deionized, and demineralized water are all pretty much the same thing: water with minerals and other things removed. These are different treatment methods to remove ionic and organic materials from water. The reason you use this type of water is to control what gets put into your cooling system. In tap water the hardness elements such as Calcium and Magnesium cause scale buildup. Things like sulfate and chloride cause corrosion problems. There is nothing mysterious here, just some basic chemistry. Some tap water is perfectly suited for use in coolant systems but it must be tested to know for sure. In most cases it is much cheaper to just used distilled water and not worry about it.
The pH of distilled or deionized water can be as low as 5.5 or so if exposed to air. CO2 dissolves in the water and forms carbonic acid. Oxygen will also dissolve in water.
You don't want to use pure water (distilled or otherwise) because it offers no corrosion protection and your system will rust like crazy. Also you need the glycol to increase the boil point and decrease the freeze point. You want at least a 40% mixture and 50% is even better. Don't go above 60% because glycol doesn't cool as well as water so your system can overheat.
When flushing your cooling system make sure the heater control is wide open (not the fan but the hot/cold) so fluid will circulate through the heater core. When draining the system you can typically drain only about 70%-80% of the system. So for example, if you had a 10 gallon that can be drained 70% 3 gallons will remain. To flush, drain it down, fill it with water, and then run without the cap on until you can see the water circulating in the radiator. Drain it again and refill with water, you now have about 0.9 gallon of the original stuff left in the system. Start it up and repeat the process. After the 3rd fill you have about 0.27 gallon of original coolant left so you will want to drain and refill a 4th time. By now you will be down to about 0.08 gallon. That's good enough! If you want to be really fussy you can flush a 5th time using distilled water and you will be down to 0.02 gallons of the original. Don't bother adding distilled water until the last flush otherwise you'll be wasting money.
It's a little tricky refilling the system because you don't know how much water is left behind. I myself start by adding a gallon of concentrate and then adding 50:50 antifreeze/distilled water mix. I continue adding until I can reach the coolant to test the freeze point. The car must run until the coolant is well circulated before the freeze point is checked. I then adjust the freeze point by adding glycol or water and then top-off the system.
As for pH, it should be well above 7. Some coolants test close to 7 but most are in the 9-11 range. Iron corrodes when it drops below 7 and aluminum corrodes when it is about 11. There is no reason you couldn't add sodium hydroxide to raise the pH, however a drop in pH most likely indicates the glycol is breaking down to form acids so it may be reaching its expected life. As for adding ionic materials that shouldn't be a problem as the additives in conventional coolant are mostly salts of sodium or potassium. If I had to pick a target I would shoot for about 9.5 yo 10.0. Just make sure you take a reading after the coolant is well circulated.
As for using a coolant recycling flush service I do not recommend this because this device only filters the coolant to remove solids. It may replenish some additives but it cannot reverse the effects of coolant breakdown. Don't let anyone tell you that coolant doesn't breakdown. The glycol becomes oxidized to form the organic acids: glycolic, oxalic, formic, etc. all of which lower pH and lead to increased corrosion. This is why you must change your coolant periodically.
Well I've rambled on enough. Hope this information helps.
Stinky
The pH of distilled or deionized water can be as low as 5.5 or so if exposed to air. CO2 dissolves in the water and forms carbonic acid. Oxygen will also dissolve in water.
You don't want to use pure water (distilled or otherwise) because it offers no corrosion protection and your system will rust like crazy. Also you need the glycol to increase the boil point and decrease the freeze point. You want at least a 40% mixture and 50% is even better. Don't go above 60% because glycol doesn't cool as well as water so your system can overheat.
When flushing your cooling system make sure the heater control is wide open (not the fan but the hot/cold) so fluid will circulate through the heater core. When draining the system you can typically drain only about 70%-80% of the system. So for example, if you had a 10 gallon that can be drained 70% 3 gallons will remain. To flush, drain it down, fill it with water, and then run without the cap on until you can see the water circulating in the radiator. Drain it again and refill with water, you now have about 0.9 gallon of the original stuff left in the system. Start it up and repeat the process. After the 3rd fill you have about 0.27 gallon of original coolant left so you will want to drain and refill a 4th time. By now you will be down to about 0.08 gallon. That's good enough! If you want to be really fussy you can flush a 5th time using distilled water and you will be down to 0.02 gallons of the original. Don't bother adding distilled water until the last flush otherwise you'll be wasting money.
It's a little tricky refilling the system because you don't know how much water is left behind. I myself start by adding a gallon of concentrate and then adding 50:50 antifreeze/distilled water mix. I continue adding until I can reach the coolant to test the freeze point. The car must run until the coolant is well circulated before the freeze point is checked. I then adjust the freeze point by adding glycol or water and then top-off the system.
As for pH, it should be well above 7. Some coolants test close to 7 but most are in the 9-11 range. Iron corrodes when it drops below 7 and aluminum corrodes when it is about 11. There is no reason you couldn't add sodium hydroxide to raise the pH, however a drop in pH most likely indicates the glycol is breaking down to form acids so it may be reaching its expected life. As for adding ionic materials that shouldn't be a problem as the additives in conventional coolant are mostly salts of sodium or potassium. If I had to pick a target I would shoot for about 9.5 yo 10.0. Just make sure you take a reading after the coolant is well circulated.
As for using a coolant recycling flush service I do not recommend this because this device only filters the coolant to remove solids. It may replenish some additives but it cannot reverse the effects of coolant breakdown. Don't let anyone tell you that coolant doesn't breakdown. The glycol becomes oxidized to form the organic acids: glycolic, oxalic, formic, etc. all of which lower pH and lead to increased corrosion. This is why you must change your coolant periodically.
Well I've rambled on enough. Hope this information helps.
Stinky
