Mike,
The 28% acetic acid is probably somewhere around the strength of some
commercial flushes which use oxalic acid. Oxalic is stronger than acetic
(ionizes to a greater degree in water). The ionization constant for acetic
is 1 x 10-5 while the first ionization constant for oxalic is 7 x 10-2.
I have used oxalic acid before to flush a system but you have to be careful
as to how much you add to the system. Too high a concentration could not be
good. I would have to work it out but I suspect that 0.2 mol/liter would be
about the limit.
And by the way, once you flush with any acid the system should be rinsed
with a neutralizer. Baking soda would do fine but once again not a great
quantity. This is then followed by water flush.
Keith Pennell
> After cleaning the radiator in my Vandan Plas, I hit upon the idea of
> cleaning the entire cooling system in the car from the inside. I figured
> that the radiator and block was probably plugged with minerals (we have
> hard water) and that was impairing the heat transfer. My solution was to
> dissolve the minerals and have a clean motor and radiator. I tried a few
> of the commercial "rad flush" solutions, and found them all equally
> inert, so I started thinking about a DIY solution. Acids dissolve the
> calcium deposits quite nicely, so I thought about various acids to use.
>
> Fortunately, my Mom works at the University and her boss is a Ph.D. in
> Chemistry, so I asked him. He said not to use a strong acid, such as
> hydrochloric or sulfuric acid, as it will eat the aluminum head, so
> things like CLR were out. He recommended acetic acid (vinegar), but with
> the caveat that it will react with glycol, so all the anti freeze must
> be well flushed first. I thought about buying a gallon jug of vinegar,
> but it is mainly water and less than 5% acid. Instead, I went to a photo
> supply and bought Kodak 28% acid, intended as a stop bath for film and
> paper processing.
>
> I drained my anti freeze, and flushed the system with water to get as
> much antifreeze out as possible. I then added the 16oz bottle of acid to
> a gallon bucket of water and poured that into the radiator, then topped
> the rad up with water. I ran the car until hot, and let it sit for an
> hour or so, then drained the acid out. It's important to have both the
> block and radiator drains open, as I got a lot out of the block drain
> after the rad came clean. I put a pan under the drains to catch the
> acid, and what when in clear came out looking like chunky milk. There
> were so many minerals that they settled out in a 1/2" thick layer in the
> drain pan after it stood for a while!
>
> Once the acid was drained, I filled the system with water to flush more
> minerals out, and to remove the acid. I repeated a few times to make
> sure the acid was gone, then replaced the antifreeze. So far the car
> runs much cooler, and is smoother. Generally it will stay right at the
> thermostat temperature without the fan running, unless I get stuck in
> traffic. Then the temperature will rise, but once things start moving it
> will cool down again, whereas before it would stay hot. This procedure
> made a big difference to the car, and was well worth spending $4.99 on a
> bottle of acid.
>
> Craig
> 64 OTS
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