Gearhead Jim

It's about time to change the coolant on our C6.

The dealer can use their power suck-fill machine, which should do a good job of getting all the old coolant out. But they say it must use tap water to mix for the refill.

Or I can have an independant shop do the drain-refill trick a couple of times, and use distilled water. But they won't get all of the old coolant out completely.

Water in our area tends to be somewhat hard, but the dealer is in a different town and I don't know exactly how hard it is.

The manual says to use clean, drinkable tap water. So that is at least acceptable. But which method is best?

Comments?

JCtx

I'd NEVER use tap water man, and even less if known to be hard. THAT's what corrodes your aluminum components over time. Like all other fluid changes, if you do them frequently enough, no need to remove every last drop of old fluid. If you wait until your coolant is a mess, then you might not have a choice. But even then, it's still better to do 2 coolant changes one after the other, than using tap water.

Bottom line is just do a regular coolant change with distilled water, and do another later on if needed. Good luck.

LS WON

When I went to dealership because Corvette has a closed cooling system, all they do is open the drain **** at bottom of radiator and let that drain out and replace it with coolant mix. No flushing involved and the way they did it you can easily do that yourself.

shaimerej

I'm sure this is going to turn into a riot but here are my thoughts. Well, before I give my thoughts, a little bit about my background. Nuclear power plant design and operations, high pressure and temperature steam and boiler water chemistry consultant. Power plant commissioning consultant.

Demin water on its own usually is more destructive than normal water. Water wants to dissolve things. Things will dissolve in water until they reach their respective saturation point. True demin water has little to no dissolved substances in it. So, employing it alone tends to lead to issues by dissolving the system you put it in. Using demin water in conjunction with chemicals is normally the best way to provide a good working fluid in extremely high energy, long lasting applications and/or systems. (power plants, not your engine) Your engine uses very little water as a coolant and should be a true sealed system. Clean, tap water contains very little impurities, even if it is hard. A small portion of these impurities may come out of solution and form coatings on your engine internals but we're talking microgram amounts. Usually, water/coolant is left in the engine for long periods of time so, these micrograms are not going to turn into grams, ounces or pounds unless you replace your coolant daily. House fixtures typically see thousands and thousands of gallons of untreated hard water before they become fouled. They do say "clean" water though. Clean means no macroscopic impurities that would have to potential to cause mechanical damage to high tolerance parts and pieces so, if you can see stuff in the water, don't use it. I'd be 1000 times more concerned about this than what's dissolved in your tap water.

Power plants employ chemically treated demin water because the amount of water in these systems (many thousands of gallons) presents the opportunity for even parts per billion (ppb) concentrations to produce noticeable amounts of plating and/or fouling. Power plant also tend to have a constant input of new water into the system though small can worsen the problem. Power plants also employ temperatures 1000 F and pressures 3800 psi (far beyond what your coolant sees) that can make ppb levels of impurities an issue.

In short, using demin water is pretty much OCD for your car. When mixed with appropriate amounts of antifreeze, won't hurt anything but the extra money is better spent on beer.

Spark 2

Just use the water from your home's dehumidifier.

Water was taken from the air. Has no minerals or chemicals in it.

HOXXOH

I used RO water when I changed it. Your bigger concern should be in the shape and size of the water passages. Even though the coolant (antifreeze) will inhibit corrosion, it won't stop erosion. I'd guess the erosion will do in your engine sometime around the 4 million mile mark, so it's wise to trade it in before that happens.

96GS#007

I've always used distilled water to flush the system. Just did that on my '96 and I ran 14 gallons through the system (1.5 - 2.0 gallons at a time. Run the engine to operating temp. Allow it to cool. Drain and repeat until the water runs clear.) I then refilled with 25% coolant, 2 bottles of RedLine Water Wetter, and topped it off with distilled water. Done this for years on many cars (aluminum and iron blocks) with no issues. FWIW, the '96 is 500hp and sees track duty.

I plan to do the same when the time comes on the new GS.

If you're concerned, perhaps buy the pre-mixed coolant/water solution and ask the dealer to use that.

Frankly, I doubt a little tap water will hurt. Maybe by the time the car hits 100k miles, you might see coolant temps up 5*.

Sunset-C6

Ask yourself do you really think GM or any other manufacture uses any thing but drinkable tap water?

HOXXOH

So here's a thought of something to try.

Save a few ounces of your current fluid and the same amount of a new mix of both tap water and distilled with coolant. Then we can find someone (maybe like Callaway) who will be changing their coolant at the 150,000 mile point to submit theirs too. I'm assuming here that you're changing at the 5-year mark and much less miles.

Send all four samples to a lab for spectrographic analysis.

The differences will show how each type of water affects the original mixture and also the results of long term low mileage vs quicker high mileage.

I feel confident that GM already did these tests, but also pretty sure they won't share their findings.

LTC Z06

regardless just buy the pre 50-50 mix.

Mad*Max

C-INRED

I'm going with the water chemistry consultant - he's probably more qualified than the rest of us put together to answer this question.

Racer

Plain 'ole water, and I will bet anybody, I NEVER have any related problems because of it.

LMB-Z

I would use water. Here is why: water has water in it. Water alone will not aid in keepin your car cool, so you should put water in it. Flush it, then flush it again, then drink a beer, then flush it again, another breer, fulsh, then addd waterrrr. When the wattre is full, another berrre.. th3en add'd anti freezwe. antoehther beerrrwee. Thjen kchechk lefveel of wattter. done.

Gary '09 C6

^

GTJim

Pinky...

I would use nothing other than premixed AC Delco/GM Dexcool.

LS WON

Buy the Amsoil coolant at $30.00+ per gallon

shaimerej

Not true. Condensed moisture from the air is not the same as demineralized/distilled water; it will have have minerals and chemicals in it. I'd suggest tap water over this as tap water is well processed and controlled. Condensed moisture from the air could have anything in it. That being said, I wouldn't expect any problems by using said water.

Rossi6998

I have a mechanic who actually works for Ford. When I have non-warranty work done on my Corvette, he is the one I go to because I trust him.

Anyway, I had my coolant changed after owning the car for three years. I bought a couple jugs of Dex-Cool and brought the Corvette to him to flush the radiator. Without me asking, he used distilled water.

If you live in the Southern California area, take a look at the lime deposits that are probably forming on faucets inside your house. I have had to replace my faucets on several occasions because of the hard water.

Having said this, I have no problem spending a few bucks for distilled water....