Chichester Yacht Club Magazine November 2016 | Page 12

Te c h ni ca l & S af e t y
Some thoughts on anti-freeze

By Ian Culley

After 14 years and some 1,500 hours of near
faultless running the Volvo 2020D engine in
my Bavaria 32 Another Fantasy developed a
problem. Although it would run quite happily
without overheating or showing any other kind
of distress it refused to pump coolant through
the hot water calorifier circuit.

inside the engine and to lubricate the water
pump.

Despite carrying out all the obvious checks:
fresh water circulation pump, thermostat, heat
exchanger matrix, header tank, heat
exchanger pressure cap and so on I could find
nothing amiss.

With this in mind we dismantled the calorifier
circuit and flushed out the feed and return
pipes and the calorifier itself using clean fresh
water. Result: problem solved and the engine
once again heats the domestic water.

In desperation I contacted the local Volvo
Penta agent, who spent some time with me
re-checking everything. After some time he
suddenly had a ‘eureka’ moment, and asked
me what kind of anti-freeze I used. Answer:
various different brands over the years:
BlueCol, Shell, BP, Halfords, Starbrite,
whatever was available.

I’ve always been meticulous when maintaining
the engine particularly with regard to changing
the engine oil, for example being careful not to
mix mineral oil with the more expensive
synthetic brands, as I’m told that sometimes
they can be incompatible.

I’d always thought that anti-freeze was
basically ethyl (or methyl) alcohol, with colour
added to make it look pretty.
Not so, he said. Different manufacturers use
different chemical formulations, some
containing additives to help reduce corrosion

Unfortunately some brands, if mixed with
others will react and form a glutinous gel
which can effectively cause blockages in the
cooling system.

I’ve learned the hard way that the same is true
for some brands of anti-freeze. Be warned!!
As an aside to this episode I discovered one
other important thing. When dismantling and
re-assembling the heat exchanger assembly,
it is vital to make sure that the large rubber
boots at each end of the heat exchanger are
installed properly and that they make a
positive seal round the internal
heat exchanger matrix.
If not, when the engine is run it
will effectively short-circuit the
fresh and sea water cooling
system and pump sea water into
the fresh water part of the system.

This will overflow from the header
tank and fill the bilge with sea
water. Very helpful!!

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