bounced. John, you need to send your posts to v12-engine@jag-lovers.org----- Original Message -----
From: “john holmes” jmholmes@sympatico.ca
To: “v12-engine-digest” owner-v12-engine-digest@jag-lovers.org
Sent: Tuesday, September 24, 2002 9:24 AM
Subject: V 12 Slow Overheating
This topic has received quite a lot of attention here lately and I have
found the discussions on hardware design and function very worthy of this
list .I believe that the reason the systems gradually loose their
effectiveness, even if the hardware HAS maintained its functionality, is
that the passage ways within are gradually being coated with some sort of
chemical deposit which is derived from the stuff that successive owners
put
into the cooling system .This coating is far less conductive to heat than
the original metal surfaces . Even if they were not adding the infamous
Barrs leaks, they were certainly adding coolant and water . By using
regular
tap water over a period of many years I believe it is possible to build up
a
sufficiently thick internal coating to hamper the correct operation of the
overall cooling system .The rate of build up of the deposit is of course
very dependent on the chemistry of the local water supply, and will be
especially quicker for so called hard water . The overall effectiveness of
the cooling system is then gradually diminishing at a barely perceptible
rate, so that at some point the cooling capability is marginal and
intermittent problems emerge, starting of course in spells of hot weather.
The radiator is then ultimately fixed either by rodding or total
replacement. However , that still leaves a substantial deposit inside the
engine block. I read that when major engine overhauls are done that
deposits
inside the block must/are removed by scrapping/chiseling etc and also by
chemical cleaning( presumabley by very aggressive chemicals by dipping in
a
tank ), so that metal surfaces are again exposed to the coolant flow.It
would seem that in some cases the deposits of crud and debris is quite
substantial. I find it difficult to believe that there are not water
treatment chemicals that when used in trained hands can dissolve out the
deposits either when used with a hot running engine or when pumped around
the engine by an external fluid pump. Hopefully we have someone on the
list
who is knowledgeable about the water chemistry of boilers( assuming of
course that it is relevant!). Although I am a retired chemist this is not
an area of expertise with which I am familiar . Do we have any takers, or
am
I off track?!John M Holmes 1973 E-Type S III Supra 5-Speed, Ontario.
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