how smooth does the water pump turn by hand ?
how good a water pump did you put on ?

20K miles is not a lot of miles on a high quality wbxr water pump,
but 4 1/2 yrs on the same coolant is a really long time.

the best way to proceed is almost always ..
dissemble and inspect carefully,
identify all tired parts replace as necessary.

I never understand why people are wondering 'exactly' what is needed
before they take it apart.
heck ..
it might not even *come apart* easily ..as 1.9 t-stat housings are very
prone to severe corrosion on the long bolts going through the housing t,
and rare is the tech that assembles them any other way than bare dray
metal-to-metal.   All parts should be well reamed and cleaned out,
cleaned of corrosion, treated well, and assembled with liberal amounts
of anti-seize.

so see how bad ( or not bad ) things are *First.* .
you may want to replace the w. pump, of course.
I'd sure put in a new t-stat, a german 80 C one,  at this time of year.

I even paint the parts with 'zero rust' paint sometimes.  They need all
the anti-corrosion help they can get. I like permatex high tack gasket
sealer on bolt threads, or anti-seize at least.
The pipe across the top of the engine is prone to pin-hole leaks as well.
I always run a bit of water soluble machinist's cutting oil as a rust
inhibitor and w. pump lube in all my vanagon cooling systems ..
your main pipes could be getting rusty too.
Even changing the coolant once  a year on this age vanagon would not be
too often. You never get all the old stuff out in a simple drain and refill.
I like Water Wetter in the coolant in the summertime too.
And you sure don't want to be replacing a front heater core if you can
help it.  They rot out too eventually.
Corrosion is the big enemy ..
internally and externally nature and chemistry are trying to send it
back, in tiny bits at a time, to the environment .
VERY easily prevented with diligence, good materials,  and solid
workmanship.

'it's not in the parts, it's in the workmanship."
scott

On 4/27/2012 8:20 AM, Walter Houle wrote:
> My 1.9 thermostat housing recently sprang a pinhole leak. Its behind the
> flanged piece that contains the short hose connection to the cylinder
> head. I suspect corrosion is the cause. I checked my records, I replaced
> the water pump 4 1/2 years ago and approx. 20,000 miles ago. Questions:
> Can I get that connector piece off without removing the water pump? If
> not, should I replace the water pump while I'm in there or just re-install
> it with new gaskets? Any advice?
>
> Thanks,
> Walter
>