I have a customer with an 87 Westie that has a cooling system problem.
The van will heat up rather quickly compared to similar vans I have
here, and then will stay at about 3/4 on the gauge.  I have an infrared
heat gun so I can run around and check the temperatures of everything.
I did this on a normal running van (needle at about center) and the
overheating van.  The only difference I can see between the two is this:

If I check the hose that is to the right on the thermostat housing (goes
to the plastic coolant distributor on the passenger side behind the
firewall), it reads around 185F on both vans.  However the difference
comes with the larger hose that comes out of the left of the thermostat
housing (short 90 deg hose that goes to metal coolant pipe).  On the
normal van this hose it around 165F.  On the hotter running van this
hose runs about 185F as well.  Also measuring temp at the coolant
expansion tank.  The normal van sees around 185-190F.  The hotter
running van sees around 200-205F.  If I turn on the front heater fan the
needle moves down a little (plenty of heat coming out of here).

I measured at the radiator (top corners) and they are running about the
same temps.  If anything the van that runs hotter has a slightly lower
temperature at the radiator.

I have recently replaced the water pump, the thermostat and flushed and
refilled the coolant system with 50/50 mix coolant on the hotter running
van.  Also has a new radiator fan switch.  Of course the system is bled
properly.

The van that runs hotter has a relatively new rebuilt engine (less than
5000 miles and I believe it is an AVP), however it did have some oil in
the antifreeze before we flushed it (I believe this was residiual from
the previous engine croaking).

I am thinking that the radiator is either bad or needs to be flushed
directly (we flushed the entire coolant system from the rear of the
van).  I think it has oily slime inside from the oil in coolant that is
not letting it work properly.  Any other opinions or advice are welcome.

I just wondered if there was a full-proof way to know that the radiator
was the culprit before going to the extra expense/pain of replacing the
radiator.

I appreciate any experience or advice you have to share.

Ken Wilford
John 3:16
www.vanagain.com