I have to a few observations on the Vanagon (1.9 liter setup) stock oil
cooler and it's failure.   When your oil ends up in the cooling system of a
Vanagon, expect a nasty job trying to get it out.   Also, you can probably
count on the Blue Cap failing and I blew a hose, till I figured the system
was not venting properly...
   I found if I parked engine-high and let tbe system  sit a while after a
flush, lots more oil, with the consistency of heavy cream, would float up
to the top of the expansion tank, then I  could pour more water in there
and wash it down through my engine space and try to hit a tub under the
van...
    I've done 5 full flushes now and a hard 100 miles shakedown... that's
when I discovered the blue cap failure.... backing into my shop takes some
finesse and by the time I got in, white goo was again spewing out as she
boiled and the fan spun.... spewing out of a hose...and the expansion tank
was...... expanded!   I could hardly get the top off to get a nice facefull
of hot white greasy oily coolant...ugg!
  Mixed oil and water is really messy.
   I was hoping all the posts about the VW and the weak oil cooler was
wrong....but mine, about two years old, went out too...When I get a chance,
I'll be taking that out and making a better setup... I never want to deal
with another failure...and I'm lucky nothing more serious resulted from it
blowing..