Joel, how about the obvious? Why not use the sender already in place? If you
have a Cockpit or other standard VDO temp gauge, that sender will work fine.
Mine is set up that way, although it's now in a different location on the TD
engine. I'd imagine you could connect both gauges to the same sender,
someone correct me if that won't work. If not, then you could possibly drill
and tap a new hole into aluminum thermostat housing for a second sender.
BTW, the drains on the heads should be 8mm x 1.25.

Karl

-----Original Message-----
 Hi everyone,
I have been contemplating the issue of guessing at the coolant temperature
for a while and I too want to install a gauge to get a more accurate reading
on this.

I have the regular VDO sender that fits on the the big hose going from the
water pump to the thermostat.  It is threaded, I believe at 8x1.00 which is
unusual for all other VW threads (usually 8x1.25 but that OK) ( This is the
common thread on an Alfa Romeo....SO!)

The three locations that I was thinking about are the following:

1) the top air plug on the radiator is the same size 8x1.00 and it fits
perfectly, trouble is that you are only getting relative temperature since
you are far from the engine. It may also not be accurate if you have an air
pocket in the coolant circuit.
This works and it is quick to install.

2) get a different sender from a BMW or other VW that will fit in the
cylinder head drains plugs. Simply remove the allen bolt (if you can) and
install the new sender.
Does anyone know the diameter and thread size of the the cylinder head drain
bolts?
I know that Fast German Auto in Santa Ana Ca makes some gallactic probe to
insert in the hole to keep the ions from crystillizing on your polished
head. (oops did I say that?)
This would be the most accurate temp reading.

3) tap the 8x1.00 (or whatever it stinking is) into the flat spot on the
plastic T section. I think that all vans have some T section to connect to
the radiator hoses.  This would also be easy to do and you would get a close
reading on the engine temp.

My three cents.
Joel
89 Syncro Westy
Rochester NY