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Deionized water for coolant? Good idea?

I work in a lab and can get deionized water. Any real advantage to using this in the cooling system? I realize most use it for batteries but I was wondering if limiting the salts would reduce corrosion in the radiator. On the other hand, perhaps manufacturers factor in the salts for the performance of their products?

Maybe a minor help, but my understanding is that most deposits in cooling systems result from corrosion/chemical reactions within the engine, not from the minerals in the water. Couldn’t hurt, though.

With great respect to Texases, many water suppies contain things that while perfectly safe to drink can cause corrosion in cooling systems, as well as minerals that can build up in cooling systems. I’ve even had well water eat completely through brand new copper pipes in 10 years. I had 16 pinhole leaks with patches when I replumbed my house in Litchfield.

But I thing you’re confusing deionized water with distilled water. Distilled water can be purchased at any grocery store for about $1/gallon, and the distillation process removes all the thing sthat can cause problems with your cooling system including the salts and minerals. I recommend the use of only distilled water in cooling systems .

  • correction made to the location in the post of “including salts and minerals”. Doggoned computer originally put the words in the wrong place!

Hi MountainBiker

If I confused deionized with distilled water, my chemistry PhD advisor back at Columbia would be very disappointed. We use deionized water in our lab work since it is easier to prepare in bulk, but both are largely devoid of impurities of all types. I ask since I can fill up all the jugs I want in the lab for the car.

I agree with you that water supplies around the US vary greatly. Our city water isn’t bad but why put in magnesium and calcium salts it not needed?

You’re right, added minerals are not needed, and mountainbike’s right to recommend distilled or deionized water. One reason I’m not really concerned is that household plumbing sees thousands of gallons of water pass by, so even slight mineral drop out can add up quickly. As long as you’re not constantly adding water to a car, it’s only that one gallon of water than could do any damage. Most tap water doesn’t have lots of minerals in only one gallon.

Point taken. And I agree that either is a far better additive to cooling systems than tap water.

Radiators still contain large amounts of pure copper and/or even aluminum (alloy unknown). I seriously doubt if radiator manufacturers compensate for minerals, salts or, or anything else not contained in distilled water in their products, or if car designers spec it in their requirements to radiator manufacturers on the Spec Control Drawings.

I agree, why chance it?

Within reason, the best quality water should be blended with the coolant. Minerals can limit the life of modern coolants to a shorter period than the original factory fill.

You will find plenty of information about the corrosive effects of highly purified water on metals. Be sure that you keep in mind the differences between that in an open system and that mixed with a proper coolant in a closed system.

True, I imagine that any pure water added to a coolant system will quickly become cleanish water and there should be no corrosive effects from pure water. I’ll bring home some gal of the stuff and see what happens. This is for a 90 Camry and so far my maintainance ideas seem to have done OK.

I always used distilled water when changing coolant. I use 50/50 mix. Cheap insurance. I was surprised how clean the indite of the 15 year old water pump was(changed during timing belt service). Regular coolant changes could be more of the reason, but again for under $3.00…

I suspect your lab water is cleaner than tap water.

Whatever kind of water you use, it quickly begins to pick up ions, dissolved minerals and metals from all the various materials it comes in contact with inside a cars cooling system. Distilled water in a radiator doesn’t maintain its purity for long…

No, but it doesn’t ADD anything unintended to the cooling system either! That’s the idea behind the distilled water.

Deionized water is recommended for use in a steam iron where the process of making steam deposits salts…in the radiator there is no evaporation hence no salts deposited…and for all the other reasons posted above using deionized water in a car radiator is unnecessary.

Maybe, but what kind of ions and what will be the effect? the passivation of the metals with corrosion inhibitors will keep the metal erosion to a minumum. If you have bad tap water, contaminants will react with the chemicals in the coolant shortening its life. Ford issued infrmation that, although their factory-fill G05 is good for five year initially, it should be used for three years after service because of water quality issues.

I am sticking to my guns though I am not a corrosion chemist or engineer. Purified water mixed in the proper proportion with approved coolant is best for your cooling system. If any boiler experts, automotive engineers, etc. want to shut me down, good because they will have better information.

If you didn’t use any antifreeze with corrosion inhibitors, you would be right. The coolant mixes with the distilled or de-ionized water and keeps if from dissolving or reacting with the metals. Impurities in tap water shorten the life of the inhibitors in antifreeze because they react with the inhibitors.

for all the other reasons posted above using deionized water in a car radiator is unnecessary.

That is fair, but only in areas that have fairly clean water to begin with. Some areas have very poor water (poor in respect to the use we are talking about) and some has abrasive materials add to it in the process of getting it ready for distribution. Considering the small cost of a couple of jugs of distilled water from the grocery, I always use it.

So, is that like eating a block of cheese and drinking a gallon of prune juice? :wink: The deionized water will always be looking to satisfy its demand for ions- hench the term hungry water. Hoping the corrosion inhibitors stop that process is a risk. With distilled water costing a dollar or less, why invite trouble? There is no way I would put deionized water into my automotive coolant especially considering the cost and risk factors. The OP will save a dollar and assume some risk.

After reading all the posts re: the recent show comment concerning “hungry water”, I am left with one basic/unanswered question. Perhaps someone out there knows for sure…?
Namely, is there something about the various distilling/deionizing processes that affects how “hungry” the water is, or is it strictly a matter of the resulting dissolved mineral salts concentration?
“Deionized” water would (technically) have zero conductivity, as read by a dissolved solids meter (which should also be a neutral Ph 7).
I should add that the purity of reverse osmosis water depends largely upon the quality of the water supply, and the sophistication/operating conditions of the RO equipment.

“Hungry water” is simply a made-up term by one of the Magliozzi brothers during a broadcast. It is intended to suggest that either distilled or deionized water has a greater tendency than tap water to dissolve potential solutes.

Don’t read any factual basis into this light-hearted quip. In fact, dissolved minerals can hasten corrosion. We all know what seawater does to metals.

In terms of your car’s cooling system, there will be little difference, if any, in results whether you use distilled, deionized, or soft tap water. Avoid hard water, that’s all.

Interesting to compare opinions from two years ago to now. This also came up several years before this one and I recall that opinions were quite different then, but I haven’t been able to find that thread using the search function.

Here’s a suggestion for SteveF- google “hungry water” and post back about the real origins of the term. That statement alone brings into question your understanding of it let alone your conclusion it is safe as coolant…