The engine needs to get hot enough (180F or more) for the contaminants that
accumulate in the engine oil to evaporate.  I wondered for a while why my
van (diesel Westy) ran so cool until I discovered that the PO had removed
the thermostat and not replaced it.  The thermostat is an essential
component of a good running engine.  In extreme circumstances (unlikely in a
Vanagon due to the unusually large volume of the cooling system) the coolant
can flow so quickly through the radiator that it does not lose enough heat,
causing overheating and engine destruction.  Even when fully open, the
thermostat provides water flow restriction to force the coolant to stay in
the radiator sufficiently long for adequate heat loss to occur.

Install the right thermostat for your year and model of van and don't scrimp
on some cheapie.

P.S.  I discovered that the radiator was completely plugged after replacing
the missing thermostat!

My 2 cents,
Mike Snow

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf
Of David Del Ben
Sent: Monday, September 04, 2000 3:10 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Engine Running cold

Hi all,
Have an issue with my engine running cold. The temperature gauge pretty
much stays o the edge of the white shaded area of the gauge.
I'm pretty confident the gauge is reading accurate as we have just passed
thru a winter here and it takes a while for the Heater to warm up and get
decent hot air from the vents. Also, sometimes, stuck in traffic, the
needle does sway more to the middle of the gauge (where it should be) and
you can feel nice hot air from the vents.

I very much suspect the thermostat is stuck open - but I've performed a
'band-aid fix' by substantially blocking of air to the radiator to try &
get it to run a bit warmer.

My question:
I've been reading on the list about the lengths people go to to put oil
temp gauges & head temp gauges and all sorts of tricks to keep an eye on
the engine (head) temps. Seems to be a critical sort of thing.
Hey - why don't I just leave the thermostat as it is and let the engine run
a little cooler. Is that going to be better for the engine? As I said -
we've just come out of winter - and I managed with the Heater as it is.

Any thoughts - anyone.

David Del Ben
85 1.9 Vanagon