Temperature reading at radiator inlet

I have been running my s3 elan, which I have recently put back on the road after 25 years of sitting. The temperature guage is running around 90c when warmed up, which is high, but when I check the temp at the radiator inlet it reads about 55c and with the cap removed and coolant checked directly, 60 ± . What should the radiator temperature be after a good run, at the fins below the inlet hose? I believe my temp guage is improperly working.
Greg

I’ve come to the same conclusion about my gauge after checking the temp at the rad neck (see http://www.lotuselan.net/forums/viewtopic.php?t=14641&start=15 if you want the full saga).

I assumed, until someone tells me otherwise(!), that the reading at the neck would be the same as that picked up by the temperature sender as the coolant flows from the thermostat housing into the top of the radiator.

My gauge reads 8 to 10deg higher than the probe I used.

if the gauge is wrong, could be the voltage regulator, or alternatively an tired gauge.
Its relatively easy to take the gauge apart and recalibrate
Tim

The temperature guage bulb is located under the thermostat & the hose to the radiator is above the thermostat.
The temperature guage will therefore show the temperature in the cylinder head.
Which is really what you need to know.
Unless the thermostat is open the temperature in the hose to the radiator will be lower.
There will also be a small temperature drop between the point where the coolant enters the radiator & the filler cap neck.
Most commercially available electrical temperature sensors have a manufacturing tolerance of about +/-2? Celsius.
Under normal running conditions with the cooling system sealed, thermostat open & normal airflow through the radiator I would expect a temperature drop across the radiator of between 7? & 11? Celsius.
John