even a straightforward thing like adding
or changing coolant becomes fraught with
Case in point:
Choosing a motorcycle
coolant should be straightforward.
Motorcycle engines are made of aluminium.
It stands to reason that if we chose a
name brand coolant that featured
compatibility with aluminium as well as 7
or 8 other metals, we'd be safe, right?
Well it turns out that
we'd be wrong. At least for Honda
motorcycles. Coolants do more than
prevent freezing and protect from
overheating. They also protect from
corrosion. Traditional automotive coolant
contains silicates as part of its
anti-corrosive additive mix. It appears
that silicates (abrasive in nature)
damage the Honda water-pump seals. There
have been a spate of Honda water-pump
failures that typically occur within one
year of having replaced the OEM coolant
with silicate-based automotive coolant.
What's the solution?
The recommended coolant,
at least for Honda motorcycles, is the
coolant. I suspect that non-silicate
coolant would be gentler on other brand
motorcycles as well.
This is sometimes an
inconvenience for someone not living
reasonably close to a Honda bike
dealership. In addition, OEM motorcycle
dealer pricing tends to be a little
higher. After more research, I ended up
buying Honda coolant from my local Honda
car dealership. This is not only
convenient, but probably a little cheaper
The product name is Type
2 coolant (as opposed to Type
1 that is silicate-based) and
comes in a 4 litre jug. It's a long-life
coolant, comes pre-mixed, is greening in
color, and contains no silicates. I found
the price reasonable and that's what I
put in. Apparently it is also available
in concentrated form. While it may be
cheaper in concentrated form, I found the
convenience of the pre-mix version to
more than make up for any possible
difference in price.
There are other long-life
coolants out there that contain no
silicates. It seems that Dexcool
(GM) has a checkered history and may be
involved in several class action suits.
Dexcool has been linked to possibly
serious problems, sometimes turning into
a jelly-like sludge. It has also been
linked to failed intake manifold gaskets.
There are enough
well-publicized doubts about Dexcool
in its applicability for automotive
applications that Id be wary of
using it in my motorcycle's engine.
Just a heads up re
switching to a non-silicate (ie
If you've been running regular
silicate-based coolant, you want to
ensure a complete flush ie get it all
It seems that silicate and
non-silicate-based coolants don't mix
well. In fact, they're considered
non-compatible. It appears that even a
small cross-contamination will impact
From what I've gathered,
two things happen.
- the coolant
performance is deemed to revert
back to the lowest one ie
a long-life coolant is deemed to
revert back to normal life ie 1
or 2 yrs.
- there seems to be
chemical incompatibility between
the two, resulting
in corrosion inhibitors falling
out of suspension. It's believed
that the acids in the organic
non-silicate coolants will tend
to cause residual leftover
silicates to fall out of
suspension. Apparently, this will
affect corrosion protection and
(how much I don't know) to
silicate-caused negative results.
re type of
water to use:
Regular, mineral-rich tap
water encourages scale build-up. Minerals
tend to deposit as scale and do so more
easily at high temperatures. This scale
will tend to accumulate at some hot
spots. It decreases heat transfer (ie is
insulating) and cuts down on the cooling
In addition, there are the
possible chemical reactions of chlorine
(common in tap water) and sodium to
create chloride salts. Jeff Bertrand
(contributor to Motorcycle Consumer News
and fellow lister) cautions that, in his
experience, this can often result in a
highly corrosive soup. Not a pretty
Though this is a normal
chemical reaction of chlorine and sodium,
I haven't researched this enough to
determine to what extent this occurs nor
what concentrations are likely to produce
negligeable or more significant effects.
What I do know is that preventing the
formation of this corrosive soup requires
a very simple and inexpensive product
that is available at every drugstore:
distilled water. A four litre jug (approx
$2) of distilled water is probably enough
to fully flush out a cooling system.
So using distilled water
is critical for both flushing and mixing.
Bruno Valeri 2003-2008