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I would say you are doing it wrong or
something is broken!

My R-TDI powered Westfalia has an massive
Audi V8 oil cooler - this is about 1m long and about 10x15 deep / high and
my oil temperatures are perfect.� My TriStar sounds a lot like your
system and it works well too.

If your oil never gets above 65C
(150F) then your thermostat is in a position where it makes the oil go
through the cooler all the time.� I run the OE water cooled oil
cooler, which I think is more correctly put as an oil temperature
regulator as it brings the oil up to temp faster and tries to keep it at
the water temperature, and a thermostatically control sandwich
adapter.� Oil filter, sandwich adapter, OE regulator, filter
flange.

Prior to installing my external oil cooler I could push
temperatures past 150C on long hills when pulling a load.� Even with
the best synthetic that is just too hot.� Now my oil is about 97C (
water is about 93C to 95C ) on the flats and pulling the same hills that
used to get 150C oil temperatures would result in 110C to 115C on vary
rare occasions.� I would say that's about perfect - you need to get
the oil above the boiling point of water from time to time to get any
condensation out of it.� Your 220F is about 105C which is not hot at
all - I start to get worried when I see sustained 120+ temps - synthetics
can do much higher than that!� 

The sandwich plate I am
running is nothing special - bi-metallic strip that goes over a 3mm ish
size hole when hot.� Purchased it from either CIP or Summit.

Photo the large Audi V8 cooler can be seen here:  

http://hasenwerk.ca/1986syncrowestfaliatdi/photossummer2008/DSC04717.JPG

David Marshall
VW Adventure Driver and BMW Adventure Rider
 
http://www.hasenwerk.ca

On Tue, February 10, 2009
17:54, John Bange wrote:
> 
> Since I've never been happy
with the way my oil temps climb above
> 220degF when laboring up
and over hills in my tool and part laden work
> Vanagon, I went
and bought an oil cooling system. The Mocal 19 row
> cooler
squeezes in nicely behind the left taillight and gets great
>
airflow. Unfortunately, I'm now seeing EXCESSIVE cooling. Even after
> roaring up the mountain pass at 65mph+ with half a ton of junk in
the
> back, my oil temp gauge barely manages to break 150degF.
Previously,
> before the oil cooler install, I'd see almost
225degF after a run like
> that. My first notion was that perhaps
the sandwich plate thermostat,
> which is supposed to close the
bypass hole at 180degF, was stuck and
> was pushing oil through
the cooler all the time. When I got to work
> this morning the oil
cooler was hot to the touch, so it's definitely
> seeing oil flow.
I'm wondering, though, if perhaps it's not the
> sandwich plate
thermostat stuck shut, but that the bypass is too
> small. It's
not a very big hole, and the cooler is plumbed with AN-10
> hoses
(a bit under 5/8" ID) which is pretty sizable. I can imagine
> 20W50 oil being thick enough to create enough of a pressure
> differential across that bypass hole that enough oil would be
pushed
> "the long way 'round" through the cooler,
reducing the oil
> temperature. Am I over-imagining, or has anyone
else ever run into
> something like this? I'll likely be pulling
the sandwich plate off and
> stove testing it in my wife's best
cooking pot this weekend to sanity
> check the thermostat, but I'm
still curious... am I going to have to
> install a manually
operated flap to block airflow to the cooler just
> so I can reach
adequate operating temperature?
> --
> John Bange
> '90 Vanagon - "Lastwagen"
> '90 Vanagon GL -
"Wiesel"
>