For the most part, aircraft engine oil coolers fall into
one of two categories: Remote mounted, or Engine mounted.
And it's easy to remember which-is-which: Continental -
or "TCM" powered aircraft use engine mounted
oil coolers - and everything else uses a remote mounted
oil cooler (with only a few exceptions).
SO MUCH FOR THE EASY PART
Remote mounted
oil coolers, though they come in many different shapes
and sizes - and are represented by hundreds of different
part numbers, are all basically similar; They mount
to the airframe (as opposed to the engine itself),
with hoses being used to carry oil to and from the
engine.
Continental, engine-mounted oil coolers
are just the opposite (in more ways than you might
expect); Yeah, they attach directly to the engine -
and therefore need no hoses to carry oil between the
cooler and the engine. Also unlike remote mounted oil
coolers, "TCM coolers" do not come in a great many "shapes
and sizes" (basically, there are front-of-the-engine
mounted TCM coolers, and there are those that mount
to the rear of the engine). Still, obtaining the correct replacement front-mounted oil cooler for your TCM engine
can easily erupt into a sizeable pain in the posterior
for the unwary.
BE VERY WARY
Far and away, Continental
type oil coolers (the front-of-the-engine mounted variety)
cause more hair loss among mechanics, and the people
who sell them to mechanics, than
any other type of oil cooler.
Here's why: There are two basic varieties
of front-of-the-engine type Continental oil coolers;
8-bolt and 12-bolt (indicating the number of bolts
required to attach the oil cooler to its adaptor plate).
Within the 8-bolt category, there are several different
oil cooler lengths available. In the 12-bolt category
there are also several oil cooler lengths available.
The 12-bolt class of Continental coolers is further
divided by the availability of what's known as Congealing
and Non-Congealing oil coolers.
Has your TCM engine had that 7th cylinder
hold-down stud modification done to it? This is something
you'll need to know in order to get the correct oil
cooler for it. The "7th Stud" mod - or the absence
of it -will determine not only which oil cooler it
requires, but also which adaptor plate and gaskets,
too. If your TCM engine is less than about ten years
old, either from factory new, or factory re-manufactured,
there's about a 99% likelihood that it is a "7th Stud" engine.
To compound the situation even further,
it's quite common to discover (after you've received
the wrong oil cooler) that the oil cooler currently
bolted to your Continental engine is not of
the same part number series listed in the parts book for your
airplane. This often occurs when, at some point in
time, somebody 'upgraded' from an 8-bolt to a 12-bolt
cooler - or from a Congealing to a Non-Congealing type
of oil cooler. Or perhaps they had that 7th stud modification
performed at the last overhaul. In any event, the important
thing to note is that there's absolutely zero oil cooler
interchangeability between the many varieties of TCM
oil coolers. And watch out; Just because an oil cooler
seems to bolt up to your Continental engine just fine,
that doesn't mean it is the correct part for your engine.
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