is the cap not holding pressure  ?
that's the first thing to consider.

if it 'does that' with 35 mph of forward speed...the rad fan is not a
factor at all.

I have seen many people think lack of rad fan function can cause
overheating at speed..
  and once you are up to 35+ mph ..rad fan is not a factor ..unless you
have a really strong tail wind ..while going up hill under load...and
that is super rare.

consider pressure cap ..
If it is' really 'boiling' find out the real temp of the boiling fluid.

consider whether exhaust gases are getting into the coolant ..
it's a pretty common failure mode.

that's why Vanagons have thatlarge rear hatch that goes up ..
so you can work on the engine in the too-often-present in Western
Washington.

I paid my dues in Port Townsend for 4 years, so I feel qualified to say
the two Key Words about Western Washington are ...

...........visiting,
and .................summer.

let us know what you figure out.
S.
On 7/22/2013 8:44 PM, Steve wrote:
> Dear List,
>
> It's odd that my temperature gauge wasn't showing signs of overheating.  First saw the leak in the back after I pulled in the driveway; the coolant reservoir of my 82 1.9l diesel was boiling over.  Checked the fuse for the fan, although i can't remember hearing it lately, the fuse looked good.  Not sure what the next step is.
>
> I may be looking for a silver lining--the weather in Seattle is amazing this time of year, usually don't get to work on this baby without the rain.  Feeling fortunate.
>
>
> Seattle
> 82 Diesel
>
> Weekender Package
>
> Seattle, WA
>