Is Distilled Water Necessary for Flushing the Cooling System?

tiger8

I'm going to have my cooling system drained and flushed. My mechanic says he refills with tap water, but someone else said that will lead to corrosion and I should use distilled water.

What is the correct answer?

Thanks.

vwracer

my new ford owners manual say use distilled water if possible

Mr_Shiftright

The header to this discussion is confusing.

Do you mean using distilled water to FLUSH the system or to FILL it?

SE92692

You should use only distilled water to fill and in flushing only. You can't completely drain the cooling system in most cars and if you use tap water some will be left to cause potential corrosion. Distilled water is cheap at 79 cents a gallon and you don't need to use much to do a single coolong flush.

ocelot1

I always use distilled water but I've never ran into one single shop that uses it.They have all looked at me like I was crazy for asking. I do listen to this car show on saturday via my local public radio station and there are two host and they say their is no need for distilled water and that using distilled might attract metals from the engine.I would guess it really depends on where you live,if your water is really hard and leaves rings on your fictures then distilled might be the way to go.Tony

knapp3

I had a radiator repaired at a local shop last fall. The mechanic there commented that he thinks people who use distilled water have cleaner radiators on average, based on what he sees brought in. Given the differences in local water standards and mineral levels, it seems like a reasonable precaution.
Chuck

xfiles

If you look at an old electric coffee kettle you can see how much calcium deposit has accumulated in the bottom of your kettle from using plain water. Well, if you start using distilled water you soon see within days all the calcium in the bottom of the kettle reabsorbed back into the water and the pot is clean again. It might not make a huge difference in extending engine life, but it certainly won't hurt. As for the rust issue, all water has oxygen which causes metals to oxidize.

My next point is a new vehicle has NO CALCIUM deposits in the cooling system, but later with poor water quality the calcium deposits build up leading to less affective cooling due to the insulating property of the calcium buildup. This means it takes longer for the hot engine to transfer its heat to the liquid water due to the calcium barrier.
Using distilled might not make a huge difference, but it definately won't hurt and is likely to help extend engine life.

Well, if that doesn't convince you, then replacing the heater core when it plugs up with calcium deposits might....and is an expensive repair unless you do it yourself. Your also extending the life of your radiator.

I do a engine flush with regular water, then I drain the water at the block. Only then I add distilled water. There is some regular water left behind to combine with the distilled water, but I can live with that.

tiger8

Thanks for the advice on using distilled water. I followed the recommendations of most here and had my mechanic use a gallon of distilled water which I brought in. He was agreeable, and if he thought I was crazy, he didn't say so.

bburton1

If you happen to have one of those water softening systems that uses salt to reduce the level of minerals and iron in your at home water-do not use this stuff-it has enough salt in it to really damage your cooling system. Have seen people talking about water with "hungry ions" - think it has something to do with the distillation process.

0patience

Is distill water necessary? No.
Is it a good idea? Yes.
Will it do much harm? That depends. Depends on the engine, the coolant and the cooling system?
Would I worry about it? Absolutely not.
You see, I do alot of marine work and most of which having cooling systems that pull directly from the water the boat or vessel is in. Salt water systems see the most, but freshwater aren't that bad.

SE92692,
If the system is backfilled, meaning that the flush and/or water is pushed out, while the new coolant is pumped in, then yes, all of the water is gone, maybe a minute is left, but it will mix fine with the coolant and the additives in the coolant are designed to counteract any problems the minute amount left may cause.

There is so much contamination in the cooling system, from casting, machining and everything else, the minor amounts of minerals in the tap water won't make a whole lot of difference.
In a battery, YES. Coolant, not likely.

Don't get me wrong, I am not saying it is a bad thing. Anything you can do to enhance the life of the engine is a good thing, just that it isn't an absolute. If you have a water softener, then distilled or another source should be used.
The chemicals and salt from the water softener system will eat at the copper in the head gaskets, which is why salt water marine engines use stainless steel in their headgaskets.
Thoroughly confused now? LOL!

ywilson

Where do you get distilled water? I have not seen any at the stores I shop.

dtownfb

You should be able ot get it at any grocery store. Look carefully, you can easily mistake it for Spring water if you aren't looking for it.

adc100

It may say Reverse Osmosis process on it.

vwracer

Worked in grocery store for 11 years. Water labeled DRINKING WATER may be filtered through reverse osmosis. Water labeled DISTILLED can only be distilled through steam process.

adc100

reverse osmosis is just as good as distilled from a practical standpoint.

ywilson

I am going to get some and change my coolant this weekend weather permitting.