Distilled water for radiators?

Aha! Finally! An area where I have some expertise!

When I lived in Litchfield NH, I was on well water in my brand new house. I used it for mix in a radiator on the old '79 pickup I had at the time. After a few years I developed leaks. I changed the radiator and used distilled water. Some years later, my copper plumbing sprung a pinhole leak. And then another. And then another. 16 pinhole leaks and temporary patches later, I had to replumb my house. It turns out that my well water passed all the regular saftey test, but was highly acidic. And yes, it eats through copper! Like the copper in radiators and plumbing.

Yes, some well water can eat through copper. And it can also contain minerals that can build up and clog the capillaries in radiators and cooling systems. I strongly recommend using only distilled water (about $1 a gallon at the grocerie store) in cooling systems. It’s worth $1, even $2, to prevent a problem.

Yup, I actually replaced the radiator because I over-tightened a clamp an broke a plastic piece. However, I did notice the difference in temperature with the new radiator, indicating that these was some scaling too. I replace the coolant every two years (about 80K miles) with distilled water and the correct OEM antifreeze. Unfortunately, it appeared that the PO had used the green generic stuff and I don’t know how frequently it was changed. It is difficult to maintain “like new” performance of radiators over the long term, so I’ll take every advantage I can get.

Well, my MG radiator (all metal) seems to be about 43 years old this year and has had a steady diet of Prestone and tap water as long as I’ve owned it. It never has overheated, doesn’t look like any significant problems. In the absence of anything factual, I think I’ll just continue on and hope for another 10-20 years…

Do whatever works for you. Mine never overheated either, but it still was not performing as well as a new radiator after only 25 years. If whichever Prestone you are using meets the OEM specs it should be OK.

Some well water is nasty. My parents had well water in RI that would eat through just about anything.

Americar, your comments only in an open system where the supply of pure water is continually being replaced. The only exception MIGHT be with ultrapure water and you are not going to buy that at the supermarket. In fact, where corrosion might be a problem with purified water, distilled is usually recommended over double-distilled or deionized.

The sponge analogy is only apt if you view it as a sponge with very, very limited capacity. Aluminum and iron solubility in pure water that is not very acidic are, very very low. As soon as you mix a little coolant with the water it is not pure water anymore and will not be acidic.

How to you get a final 50-50 mix in the cooling system? You must just drain and fill. I flush with water and that leaves plenty of plain water in the block, heater core,… In fact, about 50% of the volume in every car I have flushed. I have to add the undiluted stuff to get the right mix.

This is true. " Neutral" water is difficult to achieve in flowing water Water has a tendency to lime or corrode depending on the pH and the mineral (calcium chloride) content. Normally municipal water system process water to be slightly liming. The theory is that it is better to have your pipes lime closed over several decades than to have them start to spring pinholes after several decades – in your walls, cellar and under ground. I think it a pretty sound standard, don’t you MB?

I flush the system with tap water until it’s clear, then I do a final flush with a couple of gallons of distilled water. I add the proper amount of straight antifreeze (half the system capacity), than top it off with more distilled water. I usually have to burp the system a few times to get it completely full.

If you drain and fill at proper intervals, flushing isn’t necessary.

“If you drain and fill at proper intervals, flushing isn’t necessary.”

I’m not taking about acid flushing, just making sure all the old coolant is removed from the system by flushing water through the engine radiator and heater core. On may cars you will only remove about half the coolant by draining, more if you remove the block drain plug. Replacing only half the coolant is a waste of time, IMHO.

Yup, but if I build again I’m going all plastic! Oh, and mine started with th epinholes in about one decade.

The new systems with the inlet feeding into a manifold and flexible plastic lines running everywhere look really great. And the new polymers are impervious to the heat.

“I’m not taking about acid flushing”

Neither am I. Actually, I was responding to Beadsandbeads “How to you get a final 50-50 mix in the cooling system? You must just drain and fill.” Your reply was a good answer to his question. Personally, I alternate between drain-and-refill and flush-and-fill. I usually let the shop do the flush-and-fill job. If I did it myself, I would probably be better off using straight coolant and adding water like you do.

Yup, that’s the only way I know of getting the correct mix because you never know how much water is trapped in the block. I don’t like to just drain and refill because I like to replace 100% of the coolant every 2 years (per my owner’s manual).

If your tap water is well water, then consider DI water. If not, then the municipal authority has provided water that is low in salts and will perform well.

Some municipal water is very high in salts because there is no choice in the water supply. Take for instance CAP water in Arizona.