No bypass in any of the filters I've seen, I suspect flow just stops if they
got clogged, of course you could change the filter when you dump the
flushing oil.

I prefer to just keep doing oil changes with little time between, basically
as soon as the oil discolours, till eventually it stays clean for most of
the 5000km.

Sadly, the cooling system of the 2L-TE engined surf is just adequate when
the entire cooling system is in perfect working condition.

I know all too well from participation on the Surf lists that chasing
rainbows, magic potions and faith healing will not cure overheating....

I'm waiting for someone to point out that given the characteristics of
diesel oil that the institution of regular oil changes alone will rapidly
"de-crud" a mistreated engine, but do it in a way less likely to cause
harm than suddenly causing every last bit of "crud" to become mobile.

And yes, idling an engine for 20 minutes with a sump full of diesel will
probably not of itself cause problems, indeed the average well worn engine
would happily idle all day with NO oil in it.

The possibility for harm is that if enough crud is freed so that the
filter becomes clogged which then leads to one of two things.

If no bypass, then probably no foul-no harm because the crud didn't go
through the engine.

If a pressure bypass, or worse a non full-flow filtration system, then
you are sending the crud through the lubrication system, which as I said,
is like feeding it grinding paste.

Hence my original comment of buying a Lotto ticket if the engine survives
the experience.

Late last night I was looking through my emails and I found one sent to me
by one of the team who flew a Neptune out of Davis Montham in the US to
Australia in the late 80s.

The aircraft had sat idle (though "inhibited") since the late 60s or early
70s. After putting penetrating oil down the bores to free things up, they
dumped the oil in the tanks and refilled with a somewhat lighter oil than
the engines (R3350) would normally use (advice was sought from the
manufacturer) and after all filters were changed, they fired up the
engines, which were then run at varying speeds for 30 minutes. Oil was
then dumped and filters changed (at nearly US $1k per engine + whatever
around 40 gallons of oil per engine costs).

At that point, the correct oil was installed and the engines ground run
(again for a relatively short period of time due to the fact that the
buggers tend to overheat on the ground) prior to a brief flight. After
that flight the filters were sent for sectioning and analysis, mainly to
see if there was metal present, and if so what type, and also to check for
other chemical or particulate presence.

When all was found to be well, new filters were fitted, oil topped up and
they did some longer test flights prior to flying from West coast USA to
Hawaii and then to Townsville, Australia.

Whilst they had numerous electrical and other malfunctions, the one thing
they never worried about were the engines because they had approached the
issue of engines in largely unknown condition, that had sat idle for a
couple of decades in an intelligent, planned way designed to both not
harm the engine and give them definitive information about what was going
on inside them.

I wonder if they would have had the confidence to do two very long
over-water flights if they had just bunged in some "flushing oil", then
done an oil change, pumped up the tyres, filled the tanks and launched
into the sky. More to the point, I wonder if they would have been aviators
or swimmers.

Tony Smith

I think it stood for

I
A gree
W ith
Big
Kev

I assume yours stood for

I
D on't
U nderstand
W hat
T he
F rock
T hat
S tood
F or

Zook