[Vwdiesel] What is normal coolant/radiator temps?

[Will Taygan]

'82 1.6NA diesel Westy.  10k on full rebuild.  Retrofitted later-style
coolant system (radiator/tank/hoses)

I've been fighting with this coolant heat-up for months.  Not critical,
but I think it's not right and I want to fix it before summer.

How hot should each of the pipes flowing to/from the radiator be, and
how hot should the radiator be with the temp gauge reading 3/4?  

I get a hot/warm pipe going to the rad, a barely warm rad (20F out) and
a cool/cold pipe going back - except for the return rubber hose in the
engine compartment (which also gets the oil cooler flow.) that hose gets
quite hot - all the way up to the metal coolant pipe.  Shouldn't the
flow from the rad cool that lower return hose, even with the hot flow
from the oil cooler?  

I'm used to the Jetta which would spread heat out immediately, but with
the long coolant pipes I wonder if that doesn't happen with the Van?
WHAT IS GOING ON??

I'm wondering if I could have a blocked 1 1/4" metal pipe?? It's a brand
new radiator, and I've tried 2 used ones.

Driving on any little hill - or even accelerating on the flats - bumps
the temp gauge from 1/2 up to 3/4.  Doesn't seem to go higher than that.
Radiator gets a little warm (60F) in the upper right corner, head temps
with an IR gauge approach 200F.

My last Diesel Westy would stay just above the light in the middle
unless I was cruising up a big hill, and then the radiator would get hot
and the fan would kick on.  This one isn't acting that way.

Current van is kinda acting like a head gasket leak but has compression
of 430, 450, 450 450.  There IS some air in the system, but last time I
checked it tested negative for exhaust gases (Hmmmm....)

Replaced 3 pressure tank caps - still doesn't seem to work right with
the overflow tank??
Tried 3 different radiators.
Replaced thermostat with a tested good one.
Checked water pump.

I haven't changed the sender out and I haven't run a sewer snake through
the 1 1/4" metal pipes.  Sender seems fine, and I can't imagine those
giant pipes clogging??

If I stick an aftermarket sensor in to read actual coolant temps, where
would I read them from?

Thanks,

Will in Alaska.