[Vwdiesel] DI, DW in Rolling Stock (fwd)

[Val Christian]

The following is the simple answer on deionized water vs. distilled
water.  I asked a chemist, who tries to keep our planes flying and
his fleet rolling.  Doesn't own any vwdiesels, though.  Someday he'll
see the light.   -Val

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I too have pondered over what to use in my antique Volvo radiator.  I wonder what Mercedes and Saab recommend.

What do they use in the BIG diesels??

Maybe this is a question for "Car Talk" ??  Hehehe..
(What does "brother Tony " use in his '63 Dodge Dart???)

And those Soe-fee-yah Brothers  or is it  Soe-Fye-yah?
(I dunno if they're still on WHAM?)

Gee, I wonder if Dr Mech-a-nic would answer e-mail?

Deionized water is quite pure, but not 100%, and is usually produced by ion exchange in which the water is run throught a column of "zeolite" and other resins which hold Na ions
and exchange them for the Ca and Mg ions which create "hard water" and resulting soap scum etc.  It may also refer to RO water in which reverse osmosis is used with a fine membrane that is so fine that it allows only water through it and not the heavy and large ions as well as organic molecules that could create problems.

Distilled water is produced from steam generated in some way.

pH is a factor in corrosion as well as ion content of water.  Water used must be most compatible with the alloys in the engine.  Gasket material used may leach some soluble materials. "Pure" water will pick up ions from the impurities in the metal.

A light coating of some water miscible oil such as castor bean oil will prevent ion leaching and lubricate water pump bearings.  Buffers in the additive oil as well as in the antifreeze will control pH for a while.  Oxidation of any additive to radiator water will influence pH and metal longevity.  Complexing agents, chelates, will render some metal ions less active in solution and will influence corrosive activity.  (Remember the chemical activity chart from Chem 101?)

Heat capacity of the cooling fluid is important as well.  50% glycol is generally used because of its heat transfer efficiency as well as preparatory efficiency.  (Desert dwellers should take note!).

All the above are generalities and useful knowledge.

I don't know specifics around pH and ion compatibility for alloy or cast iron engine blocks.  We checked military vehicles for pH and dissolved material content.  I can't remember any numbers.  Anti rust and water pump lubes (Castor oil) were occasionally added, but the radiator fluids were changed infrequently.

I will bounce this back to you and to a few other "antique car" aficionados (In BCC
mode for anonymity) in case they want to correct/modify this old man's statements.

Comments car fans?  What works for you?

George (Keep 'em rollin'!) Braidic