Dear Hosers (and especially Tim):

Having experienced reduced heater output, possibly from liberal additions of 
BarsLeak and AlumaSeal i will be flushing cores this spring.  Here 
are some thoughts:

You can do just the cores themselves.  I've done this on both my '85 
and the '87.  I do this because the thought of gallons of 'aggressive 
cleaners' circulating thru my leaky system makes me nervous.  It is a 
little equipment intensive but with some scrounging most people have 
enough junk around to accomplish this.  well, if you live like 
someone akin to Red Green (who will be in Bemidji on Saturday).

-disconnect heater hoses as they attach to engine.  location varies 
by year but are fairly easy to get to.
-hook up a circulating pump, a vat in which you can heat a large 
quantity of liquid, and a propane burner.  i use a 10 gallon boiling 
vessel, a 170K BTU burner, and a 12v pump.
-fill the keg with a few gallons of water, dump in your favorite 
chemical, light the burner, and let this circulate a few hours.
-flush well with clear water.
-lastly, i have a garden hose adapter that also allows bursts of 
compressed air to be shot in the water stream for dislodging 
contaminants.  it has a stepped nozzle for fitting a variety of 
heater hose diameters and a schrader valve to jet  the air in with a 
tire chuck.  it seems to loosen some crud.

this has worked well for me, though it borders on techno-geek.  the 
service manager at VW here in town asked me how to get more heat out 
of the Vanagon and i detailed this.  he just shook his head.

Alternatively, you can elect to do the whole system.  However, be
forwarned that many cleaners foam and can create a headache for you
as the radiator air-locks with foam. yes, this is the voice of
experience.   it is also difficult to flush out the cleaners from
the wasserboxer's 19+ liter system.  installation of a flushing T in
the heater loop would facillitate this but some people are
experiencing failure of these T's.  i think i will install one
anyway.

Chemicals.  I have read an article that discouraged the use of Oxalic 
acid, this is the cleaner in the powdered Prestone 2-step cans.  I 
used this before i read the article and it did no harm.  i will check 
that article again to see what the specific problem was with it.  but 
i seem to recall that it wasn't effective on solder bloom.
actually, since the vanagon uses an aluminum based  cores, 
solder bloom is not a factor in the radiator or heater circuits.  
essentially, we want a degreaser/emulsifier/cleaner.  i haven't yet 
decided what product to use.  the cans are not very descriptive as to 
their active ingredients.

One thought.  some cleaners are organic based.  maybe, just maybe one 
of these would react with the neoprene head seal, swelling it and 
stopping our leaks.  huh?  ya think?  not likely.  might try one this 
time though.

-dan